The Brigand of the Air

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THOMAS CHARLES BRIDGES
(WRITING AS CHRISTOPHER BECK)

THE BRIGAND OF THE AIR

ILLUSTRATED BY WATSON CHARLTON

First published by C. Arthur Pearson, London, 1920

This e-book edition: Roy Glashan's Library, 2020
Version Date: 2020-04-28
Produced by Keith Emmett and Roy Glashan

All content added by RGL is proprietary and protected by copyright.

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CHAPTER I. UP AGAINST IT!
CHAPTER II. WHEN THE ENGINES STOPPED
CHAPTER III. THE BRIGAND BELOW
CHAPTER IV. DERRY'S STRATEGY
CHAPTER V. THE FIRST BOMB
CHAPTER VI. THE PIRATE TRIES AGAIN
CHAPTER VII. THE MAN IN BLUE
CHAPTER VIII. THE NEW ENGINE
CHAPTER IX. HELD UP!
CHAPTER X. THE COMING OF THE SEAPLANE
CHAPTER XI. WELCOME NEWS
CHAPTER XII. THE SECRET ROOM
CHAPTER XIII. A BLIND ALLEY
CHAPTER XIV. THE SECOND YARD
CHAPTER XV. THE LONELY DOWN
CHAPTER XVI. HIDE AND SEEK
CHAPTER XVII. THE MESSAGE
CHAPTER XVIII. A DRAWN GAME
CHAPTER XIX. THE TRIAL TRIP
CHAPTER XX. MR. SEBASTIAN'S REAL NAME
CHAPTER XXI. DISGUISING THE DIRIGIBLE
CHAPTER XXII. IN TOUCH WITH THE ENEMY
CHAPTER XXIII. THE UTTERMOST HEIGHT
CHAPTER XXIV. THE END OF THE CHASE
CHAPTER XXV. THE CLUE
CHAPTER XXVI. THE MINE MOUTH
CHAPTER XXVII. THE MAN WHO VANISHED
CHAPTER XXVIII. THE GUARDIAN OF THE ISLAND
CHAPTER XXIX. IN THE HEART OF THE ISLAND

CHAPTER I. — UP AGAINST IT!UP AGAINST IT!

FROST had set in earlier than is usual even in the Midlands of England, and in spite of the fire in the stove, the little wood and iron office in which Derry Holt was working on that bitter Christmas Eve was desperately cold.

Derry sat at a roughly-made desk, with a pile of papers before him, and as he went through them his thin, clever face grew more and more gloomy. Since his father's death, the responsibility thrown on his young shoulders had been very heavy. Just at present it was almost more than he could bear.

There was a hurried step outside, the rickety door banged open, and in burst Ned Barlow, Derry's cousin and partner.

Ned was big and powerful as Derry was slim and slight. He was fair as Derry was dark. The two, though the same age, were the most complete contrast, yet perhaps for that very reason the best of friends.

"Hullo, Derry, old chap," cried Ned, in his big, deep voice. "Beastly cold, isn't it? Why don't you keep a better fire?"

"Because there's only one scuttle of coal left, and the coalman has shut down on us, Ned."

"Stingy old Hunks!" replied Ned. "Never mind. We'll chop up some of the old wood in the hangar to-morrow. Bless my soul, we're not going cold on Christmas Day. By the way, here's a Christmas present for you. Catch," he said, and flung a parcel across to Derry.

Derry caught and opened it. Inside was a pair of thick leather flying gloves with deep gauntlets, and snugly lined with wool.

"Ned, it's frightfully good of you. But they must have cost a heap, and you know you want boots."

"Bother the boots! I'm having the old pair cobbled. Anyhow, you do all the work, and the least I can do is to try to keep you warm."

"Nonsense! I couldn't get on a day without you, Ned. But I'll keep the gloves, and thanks a thousand times. I only hope I shall have a chance to use them aloft."

"Not with her, Ned. The trouble is with us. See here!" He pointed to the stack of papers. "Here are bills amounting to pretty near three hundred pounds, which is just three times the amount we have in the Bank."

"Phew, I hadn't a notion things were as bad as that. But a cargo or two would put us right."

"And where are we going to get a cargo between now and New Year. This railway strike in the Midlands has knocked things endways. There's nothing doing in Marchester or anywhere round. All the wholesale houses are closed, and most of the shops."

"It will last a week, anyhow, and so far as we're concerned that's long enough. The Pearl Petrol Company has written to say that if our account is not settled by the last day of the month they will take proceedings."

"They'll file a lien on the Air Barge, and that means she'll be locked up and no more use to us than a block of stone."

"Can't we pay the Pearl people, and let the rest stand over?" suggested Ned, whose face by this time was almost as grave as Derry's own.

"Can't be done, Ned. Their bill is £140. That's more than the whole of the balance, and I'm not going to leave the men without their pay this Christmas week."

"Well, hardly," said Ned. "But I say, Derry, this is rotten. Surely those Pearl people know we're honest? We always have paid up. Won't they give us time?"

"Not they!" returned Derry hotly. "They're a soulless Corporation, but they've got sense enough to know a good thing when they see it. The fact is that Murdoch, that man who owns so much stock in the Company, wants to get hold of the Air Barge. He tried to buy it from Dad long ago, or rather tried to buy the secret of Dad's engine, and Dad refused to sell. Now he has his chance. He'll make the Company close down on us, there'll be a forced sale, and he'll buy our airship at his own price."

"This is a peach of a business," he said slowly. "I'd no notion we were in such a mess. Can nothing be done?"

"My dear chap, I've been racking my brain for an hour past, and can't think of any scheme."

"I thought of that. But how can we? To-morrow is Christmas, then there's Boxing Day, and everything is shut for the holidays. I don't know anyone to go to. Do you?"

Ned shook his head mournfully, and silence fell in the little wooden building, broken only by a faint crackle from the stove.

He jumped up and opened the door, and in came a man. A short, squarely-built man of perhaps forty-five. The enormous fur-lined overcoat he wore made him look simply huge. But it was not his coat or figure which the boys stared at. It was his head. It was the finest head either of them had ever seen anywhere, with a great dome of a forehead, a big Roman nose, and piercing blue eyes under thick, shaggy eyebrows.

"You are Holt?" began the stranger, in a voice so deep that it was like the note of an organ.

"I am, sir," replied Derry quietly, but inwardly he was wondering what was coming next.

"Is she good for a two hundred mile trip now—this minute?" was the startling question.

Ned stared open-eyed at the strange visitor, but Derry was—outwardly at least—perfectly cool.

"It's this way," explained Derry quietly. "We can do seventy in still air. But the wind is northeast, and above the thousand level is probably blowing twenty. So, if you wish to go northwards, we can travel no more than fifty; whereas, if you desire to go south, we can cover the ground at ninety."

"It's north I want to go," answered the other. "But fifty miles an hour without stoppages will beat the average express and double the speed of a touring car. All I wish is to be at my destination before daylight to-morrow morning."

"It's not half-past nine yet. We ought to get away before eleven and land you at your destination by three. It may be a little later if the wind strengthens, but I think we can safely promise to be there before daylight."

"It won't quite run to that," laughed the other, taking out a pocket-book. "Here's half down as a guarantee of good faith," he said, and slapped five ten-pound notes on the table. "Now get a move on you."

CHAPTER II. — WHEN THE ENGINES STOPPED

FOR the next hour it was one desperate drive of work. To get a dirigible out of her hangar is never an easy task. Luckily the night was clear, and at ground level there was hardly a breath of wind; it still wanted ten minutes to eleven when Air Barge No. 1, as her owners called her, lay in the open ready for her journey.

The stranger was waiting, and with him a porter who had an enormous sack on a truck, and also a small portmanteau. These were soon slung aboard, then their owner climbed actively into the middle gondola, the boys followed with their crew of two men, and the signal was given to cast off.

A few moments later the long, cigar-shaped craft lifted quietly into the air. As soon as she was clear Derry gave the signal to start the engines, and their rattling roar awoke the echoes of the frosty night.

Her blunt nose swung round till it pointed north-east, and the rush of air past the windows of the gondola told that the journey had begun.

Derry, who was navigating, looked round to find his passenger standing beside him.

"Where to, sir?" he asked, as quietly as a cab-driver would ask the same question of a fare.

"Shorn Fell, in Yorkshire," answered the other, in his deep voice. "Make for Buxton. That will give you the exact direction."

Derry nodded. The roar of the engines made conversation difficult. Not so difficult, however, as in an aeroplane for the gondola, which was a long, narrow cabin, somewhat of the size and shape of the interior of a motor-'bus, was completely inclosed, so cutting off not only the chill of the outer air, but something of the monstrous roar of sound from the great Holt engines.

The passenger spoke again, and with his mouth close to Derry's ear, the latter could hear him quite well.

"About sixteen months, sir. My father bought this craft. She was one that belonged to the Government, and was sold for passenger service after the war. We put our own engines in and began as soon as the restrictions were lifted."

"It did at the beginning. But the strikes have hit us hard, and people don't seem yet to realise what a pull it is to be able to send a ton or so of valuable cargo across country as quickly as we can take it."

"It must be useful on occasion," replied the passenger thoughtfully, and, going to the window, peered out. "Snow on the ground," he continued. "All England's white. Holt, this is a wonderful way of travelling. D'you know, I've never been up before."

"Why not? I am a judge of character, and I trust my pilots. Now I will go to my cabin. Call me when we pass Buxton."

The sliding door had barely closed behind him when Ned Barlow came quickly into the car. His cap and goggles were rimmed with frost. One glance at his face told Derry that something was wrong.

"The aft engine is heating badly," he said curtly, "and I am afraid the others are going the same way. It's the oil—the oil we got at Marchester. Green vows there's emery or something in it." Derry paled a little, but recovered in a moment.

"We must stop her," he answered; "stop her and drain the oil out of the sumps. Thank goodness, we still have a few gallons of the old stuff aboard."

"It's blowing twenty," replied Ned gravely. "Where shall we be by the time we've finished?"

"Not too far west to make up before morning. Quickly, Ned; it's our only chance."

Ned nodded. His face was set like iron. He knew, just as well as Derry, how much depended on the success of this journey.

"Who could have played such a vile trick upon us?" groaned Derry, as Ned hurried aft. "For a trick it is. Emery powder doesn't get into oil by accident. And the damage is done already. It will cost goodness knows what in repairs."

A moment later the engines stopped, and the big airship drifted silently like a bubble down the wind.

Derry hurried out to see what help he could give. The car had a port in the roof, by which the cat-walk was reached. As Derry stepped out into the biting chill he stopped short, listening. It was the deep drone of an aeroplane engine which he heard, and, wondering who could be aloft this bitter night, he looked round for the navigating light.

He could see nothing. This puzzled him; but it was possible that the plane was hidden from his sight by the vast bulk of the envelope overhead. The sound grew louder. It was actually overhead.

He hurried up the ladder leading between the gas-containers to the observation platform above. As he emerged on the great rounded upper surface of the Air Barge the roar was deafening; but, to his amazement, it was not a plane—it was a dirigible like the Air Barge, though smaller and of a strange shape, that was driving up astern. While Derry stared, hardly able to believe his eyes, she slid right up over the Air Barge, then cut out her engines.

Before Derry could recover from his astonishment at these extraordinary tactics, a voice boomed out from above through a speaking trumpet—a harsh, rasping voice, cutting the frosty air like steel.

"This isn't April Fools' Day," retorted Derry. "Shift out of this and get about your business."

"This is my business," came the voice, harsher than ever. "Do as I say, or take the consequences."

Derry's heart sank a little. There was something ominous about this strange craft hovering like a great bird of prey overhead. There flashed across his mind stories he had heard of an air pirate, who was said to have held up and robbed several cargo planes and dirigibles. He had not given this a second thought at the time, but up here, over the wild moors, in the silence of the winter night, anything seemed possible.

Derry fled back down the ladder. If this madman were really in earnest, the Air Barge had one chance and one only.

As he dropped down into the car he got a fresh shock. A stranger met him, a man wearing a sleeved cloak of scarlet trimmed with white, and on his head a great cap of the same material. Baggy blue trousers and high boots completed the costume.

Instantly Derry recognised the voice. It was his passenger got up as Father Christmas.

"Not much merry about it," Derry answered curtly. "There's a chap in an airship above who swears he'll crash us if we don't put you over in a parachute."

The passenger stared a moment, then, seeing that Derry was in earnest, stepped to the window.

"You can't see him. He's above," said Derry. "Stay where you are. I'm going to let out gas and drop. Our engines are damaged, and that's our only chance. And here's a parachute. Put the loop around you, just in case of accidents."

"Looks to me as if I should be late for my appointment," remarked the passenger calmly.

But Derry was gone—flying to tell Ned of what was up. In two sentences he explained what was afoot.

"I've my pistol aboard," said Ned swiftly. "Case of blessed be he that gets his bullet in first."

Derry had no chance to remonstrate. Before he could do anything shots rattled out. Next instant there was a whizzing sound, a roar, a great glare overhead.

Like all good captains his first thought was for his passenger. He tore recklessly back into the car. Father Christmas already had his parachute belt fixed around his body.

"Right! I suppose I mustn't think of my bag of toys. I'm sorry for my kids, though. Well, here goes! Another new experience."

"Don't be scared if you drop quickly at first," Derry warned him. "She'll open out all right in a second."

"Now for Ned!" panted Derry, and hurled himself through the opening in the roof.

The great dirigible was blazing fiercely. The icy night was lit with a tremendous glare.

CHAPTER III. — THE BRIGAND BELOW

"Come on!" cried Ned, making a grab at him. He was too late. Derry had swung down into the cabin and seized the sack belonging to the passenger. Big as it was, it was no great weight, and, hauling it to the window, Derry attached it to a spare parachute.

"You're a fool," snapped Ned, who had followed him, "risking your life for a parcel of toys!"

With an impatient exclamation, Ned seized the great sack in his strong arms and flung it out.

The whole business had taken but a few seconds, yet short as the delay was, it might very well have been fatal, for by now the whole of the big dirigible was ablaze, a great comet of flame lighting the district for miles and miles.

Derry and Ned, together, flung themselves out of the window of the gondola, and went dropping like plummets into the depths of icy space beneath. Then Derry felt the sharp check which told him that the umbrella-like top of his parachute had opened, and as the speed of his descent slackened, he looked up and saw that the immense mass of burning wreckage overhead was beginning to drop.

His heart was in his mouth. Once, in France, he had seen a sausage balloon, fired by the Huns, fall full upon its late occupant, who was escaping by parachute—seen him enveloped in the fiery mist, and destroyed as utterly as though he had been plunged in a blast furnace.

And now a similar fate threatened him; Ned, too, for Ned was a little below him, and not far away.

Neither could do anything to help himself. They floated downwards, swinging to and fro at the end of their ropes, absolutely at the mercy of every drift and current of the freezing air, while the dirigible, falling faster than they, came nearer every moment.

Derry looked downwards. They had drifted rapidly over a small town towards some snow-clad moors, and these were still a thousand feet below. Every gorse bush showed up black against the ruddy snow. It would be a matter of nearly two minutes before he reached it. Long ere that, the blazing mass above must overtake him and scorch him to a cinder.

Another moment and it was so near that he could feel a puff of fierce heat beating down upon him from the vast reservoir of hydrogen gas which flamed so fiercely.

Lost, too, he would have been, but that at that moment the dirigible, which had been falling on a more or less level keel, suddenly tilted. Her bow swung down at a steep angle.

At the same moment a puff of wind caught her stern as it rose, and tilted her clean over. She did a sort of gigantic somersault in mid-air, then, with a heavy explosion, burst into two parts, which fell separately, each clearing the two boys by a matter of fifty or sixty yards only.

Derry watched the pieces fall, and, breaking into a rain of fiery wreckage, drop hissing into the snow. Then, as darkness fell again, lighted only by small fires among the wreckage, Ned's voice came upwards.

"The pirate chap, you mean?" answered Ned, speaking as serenely as if his feet were planted on firm ground, instead of dangling in empty air. "Never mind, Derry. We've got out of it alive, and some day we'll square accounts with our persecutor. Can you see him?"

Ned made some reply which Derry could not catch. Another puff of wind had caught the latter's parachute, and was carrying him rapidly westwards. He could just see Ned a long way to his right.

The ground was very near now, and Derry bent his legs for the shock of landing. Although a parachute seems to drop slowly, it really falls a great deal faster than might be imagined.

Derry wondered for a moment whether Father Christmas had thought of that. But the snow would break his fall unless he had the ill-luck to drop on a rock. Derry hoped he was all right. He could not help liking the plucky Father Christmas.

Next moment his feet struck ground, and he found himself sprawling in six inches of wet snow. He was up again in a flash, and rapidly unbuckling the heavy belt of the parachute. He was a little out of breath, but quite unhurt.

He looked round quickly. Ned must have come down a long way off, for he could not see him.

Derry had dropped on soft, boggy ground. He could feel it squelch beneath his feet. Then he saw that he had just missed a small brook which ran deep and dark between banks of black peat. The stars were reflected in the inky water.

On the far side of the brook was a biggish drift, and in this lay a dark mass which, as Derry stared at it, he saw was moving. A bit of the wreckage flared up, and shone upon a red cap.

"Father Christmas himself!" exclaimed Derry. "What luck! At any rate, he isn't hurt."

"Are you all right, sir?" he asked. "Here, I'll give you a hand. Not hurt, are you?"

"Not in the least," answered the other, with a cheerfulness quite wonderful in the circumstances. "Luckily for me, I dropped exactly into this drift, where I have stuck. But it is not warm, and I should be glad if you would help me out."

It was just as Derry got hold of his passenger, and started to help him out of the drift, that he saw the lights. Not more than a couple of hundred yards away twin glaring eyes came rushing across the moor.

"I don't know so much about that," Derry answered quickly; "for all we know, the driver is in league with this pirate chap who fired us."

"I did not think of that," answered Father Christmas; "but now you mention it, it seems extremely probable. Yes, I hardly doubt it. He is here to collect the ransom which our friend above was after."

"The car has stopped," said Derry, tugging at the big man. "There are two people in it. They are getting out. They are coming towards us."

"And we are defenceless," returned the other wearily, "and your friend Barlow is not within hail, nor the mechanic, Green. This is awkward. What are we to do?"

With a final haul, Derry managed to free his fantastically dressed passenger from the drift. His mind was working like lightning, for already he could see the two figures who had left the car, moving towards them, black against the white snow.

"I have it," he said. "Off with that cap and coat, sir. Trust me; I'll fix them."

With wonderful quickness the other divested himself of the tall red cap and brilliant scarlet cloak. While he did so, Derry was swiftly piling up a cone of snow. Seizing the cap, he stuck it on top of the cone, then flung the coat around it. In the pale light it looked just as if the big man were still there, stuck in the drift.

"Now get behind that gorse bush," whispered Derry. "Keep well down. Don't let them see you."

A low chuckle told him that the stout gentleman fully understood, and with surprising quickness and agility, the latter slipped away and ducked down under the gorse bush indicated, where Derry joined him in a moment.

Peering round the corner of the hush, Derry saw enough to realise that his suspicions were justified. The big, raw-boned man who came striding through the snow towards them carried something in his hand which glittered faintly, and which was either a pistol or a heavy metal spanner. His companion, a short, squat fellow, laboured along a good way in the rear.

Derry's jaw tightened. He was sick and savage at the loss of his big dirigible, and if this fellow were really in league with the air pirate, meant to do his best to get a little of his own back.

He saw his way to doing so, too, and the only thing he feared was that Ned might crop up just at the critical moment, and scare his bird out of the trap which he had set.

But there was no sign of Ned just yet, and the tall man was getting closer every moment. He had certainly seen the figure in the drift, for he half turned, beckoned impatiently to his follower, then strode on faster than before.

Now he was so near that Derry could actually hear his boots creaking through the damp snow.

Derry poised himself like a cat ready to jump. Though much smaller and slighter than Ned Barlow, Derry was extremely strong and active.

"Got you, Father Christmas!" he said, with a nasty chuckle, and reached forward to seize—as he thought—Derry's passenger.

CHAPTER IV. — DERRY'S STRATEGY

It was the chance for which Derry had been waiting. Like a stone from a catapult, he launched himself from under the gorse bush, and, landing almost on top of the big man, placed the palms of both hands under his shoulder blades, and gave one mighty shove.

The other, taken entirely by surprise, blundered forward through the drift and on to the slippery slope leading down into the brook. His feet shot from under him, he lost his balance, and with a yell of anger and surprise, whizzed downwards in a sitting position, straight into the muddy bed of the little water- course.

The water was nothing—not more, perhaps, than a foot deep—but the mud was a very different proposition. It was black and sticky, and before he knew what had happened, the bandit found himself well over his knees in it, and fastened as firmly as a fly on a sheet of sticky flypaper.

For a moment he was too surprised to speak, but when he did get his breath back, he made up for his silence by a flow of language warm enough to melt the snow, while he plunged and writhed like a speared eel.

Simon, if that was his name, paused uncertainly, then, seeing only a boy, gave a hoarse growl, and came on again.

Derry waited. His blood was up. He felt quite competent to tackle this fellow, who was clearly half-scared already.

As a matter of fact, he did not have to. As the fellow came blundering up, Father Christmas, who had been lying doggo behind his bush, shot up like a Jack-in-the-box, and with surprising activity for a man of his bulk and age, caught the astonished Simon around the body, tripped him, and sat down heavily on top of him.

"Serve you right if I sat here the rest of the night, you cowardly ruffian," observed Father Christmas calmly. "Holt, give me a piece of cord, or a handkerchief will do, and inform that man in the brook that, if he cannot restrain his language, I shall deal with him severely."

In spite of everything, Derry laughed. He couldn't help it. He had lost everything he had in the world, yet the whole business was so comical that he found himself chuckling whole- heartedly.

"You're pretty cheerful, considering everything, Derry. Who in sense have you got here?"

"I was after old Murston's money," he roared. "Now I'll have more. I'll skin the lot of you! I'll make you sorry you ever were born! I'll—"

"You'll stay where you are till you're sorry you were born," cut in Derry sharply, "that is, if you don't shut that foul mouth of yours. Dry up! I mean it."

The fellow subsided. He was just beginning to realise the tightness of the place he was in from every point of view.

"It is, my young friend," put in Father Christmas, or, rather, Mr. Murston, as we must now call him. "It is exactly what we want, and with luck we may reach Shorn Fell in time, after all. The only question is, what to do with our prisoners."

"We must take 'em along," said Ned. "Can't leave fellows like that to work their wicked will on the world at large."

"Quite so, Barlow," agreed Mr. Murston. "But there are five of us, and we cannot tell whether the car will hold more than four."

"We'll stuff 'em in somewhere, even if we have to use 'em as footstools," laughed Ned. "Come on, Derry, let's get our long friend out of the brook."

"Better tie him first," suggested Mr. Murston. "He seems to be a person of a somewhat violent temperament."

"We'll need a rope to haul him out," cried Ned. "Tell you what; we'll get the one off your parachute."

No sooner said than done. Ned had the rope clear in a twinkling, made a noose at the end, and flung it round the big man's body.

It took all three of them to haul him out and when he did come, like a tight cork from a bottle, he was black slime to the waist, and so thoroughly chilled that he could hardly walk. He was tied up without resistance.

By this time Green, the artificer, had joined them. He had dropped a long way off. A keen-faced Cockney and devoted to his young employers, he was furious at the loss of the Air Barge, but delighted to find that two of the pirate gang had been captured.

The four marched their two prisoners up through the snow to the car, which stood on a road running right across the moor.

"That's our direction," said Mr. Murston, pointing. "I don't know the road, but I do know the lie of the land. Shorn Fell cannot be more than twenty miles from here."

"This here car won't make much o' that, sir," laughed Green, who already had the bonnet open, revealing a big six-cylindered engine. "Now then, let's dump those lumps of rubbish in on the floor at the back; then I reckon I can get you where you want to go in something under an hour."

"The sooner the better. I am somewhat chilly," observed Mr. Murston. "But where—where is our young friend Holt? He seems to have disappeared."

"I know what he's after," he said, and plunged away in the direction in which Derry's footsteps showed across the snow.

"So Barlow also has deserted us?" said Mr. Murston. "This is curious. I think that I will get inside, and wrap myself in one of those rugs with which the car is, I see, provided. That drift into which I descended has left me in a very moist condition, and my trousers are already caked in ice."

He clambered in, and Green began to overhaul the car, to see that the radiator was full and that there was sufficient petrol in the tank.

Some five minutes elapsed; then from across the moor came a cheerful shout, and Ned and Derry were seen approaching, carrying something bulky between them.

"Upon my word!" he declared; "those boys think of everything. I do believe they have my sack of toys."

"I am very much obliged to you," said Mr. Murston. "I only fear that they must have suffered in their hurried descent."

"Not a bit," returned Derry. "I put them on a parachute. They're a bit damp, but I don't believe that any are broken."

"You stayed to attach a parachute to them? Indeed, I am very greatly indebted to you," said Mr. Murston, and there was no doubt that he was grateful. "The children, too, will be delighted. Now let us proceed."

The two prisoners were dumped into the tonneau, which was large enough to hold half a dozen. Derry got in beside Mr. Murston, and Ned alongside Green, who took the steering wheel. Green pressed the self-starter, the engine roared into life, and the big car glided away down the long, straight road.

"Straight over that hill, Green," he directed; "then you must keep to the right. But I will give you fresh instructions from time to time."

"She pulls well," observed Mr. Murston to Derry. "Upon my word, we must have got out of our troubles a great deal better and more comfortably than might have been supposed."

Derry did not answer. He was staring upwards, and his face wore a very serious expression.

"If we are out of them," he remarked suddenly. "What do you mean by that, Holt?" asked Mr. Murston.

"I mean that our sky pirate isn't so far off. I can see his airship against the stars."

"I should think that is exactly what he does mean to do," answered Derry. "Yes, there's not a doubt about it. Here he comes!"

CHAPTER V. — THE FIRST BOMB

DERRY was right. The long narrow shape of the brigand's airship was clearly visible against the stars, and the loud clatter of her engines was plainly heard above the throb of the motor-car's 40-horse power. She was coming right back over the road.

"The skunk!" growled Green. "How do you reckon he's found out what's up, sir?" he asked of Derry. "He couldn't have seed much from up there?"

"We must be travelling in the wrong direction," Derry answered. "The wrong one, I mean, go far as he is concerned. That's what has roused his suspicions. He means to find out what has happened."

"She's all out now," replied Green. "It's this here hill. It's steep, and no mistake, and 'tisn't any small load she's pulling, either."

"That true. I'm afraid there isn't a dog's chance of reaching the top before he's on us."

The roar of the engines of the pirate craft was deafening, as the long, slim airship came shooting up. Another moment and she was right overhead. Then, in a flash, the darkness of the winter night was cut by a blinding beam of brilliant light which turned the snowy moor to a dazzling whiteness, and showed up the car and its occupants as clearly as the noonday sun.

"A searchlight!" gasped Green, as he crouched lower over his steering-wheel. "By James, it's enough to blind you."

Derry tried to look up, but the intense glare dazzled his eyes. All he knew was that the pirate craft was straight over them, and only a few hundred feet up. He felt like a mouse cowering under the outspread wings of a hawk.

"He daren't start shooting; that's one point in our favour," Derry answered. "If he does, he'll slay his pals as well as us."

"He'll not shoot," added Mr. Murston, confidently. "It's my money he wants, not my life."

It flashed across Derry's mind that his passenger must be a man of considerable wealth and importance, but the thought was only momentary. All his thoughts were occupied with wondering what was going to happen next.

From time to time the dazzling searchlight swung away from the car, and lit the snowy landscape ahead.

Green was doing all he knew to get the car to the top of the hill without dropping back into first gear. But the slope was very heavy, and she was not doing more than fifteen, while the airship, of course, could go quite four times as fast.

For the moment, however, the pirate was moving comparatively slowly. Judging by the pace at which the searchlight's beam travelled, the airship's speed was not more than double that of the car.

Suddenly the roar of the airship's engines ceased, and the silence of the chill night was broken only by the chug- chug of the labouring engines of the car.

From above came a voice. Directed through a megaphone of great size, it reached them quite clearly:

"Your last chance, Holt! Pull up, drop your prisoners and your passenger, and you can go on."

"You won't obey!" came the thin voice from the air. "On your own heads be it, then."

With that, the great engines clattered out again, but even then their roar did not drown a thin, whizzing sound.

The words were hardly out of his mouth before there was a stunning explosion. About a hundred yards ahead of the car a fountain of fire leapt into the night. Earth, stones, even large rocks, were flung high into the air, to fall crashing in every direction.

So great was the blast of the explosion that the car shivered and shook as though she had run into something solid. She swerved, and was almost off the road before Green got hold of her again.

"He was not trying to hit us," said Mr. Murston, from behind. "If I mistake not, his idea is to wreck the road, and so prevent us from getting on."

"No," retorted Derry sharply. "Only half the road is gone. There's room to get by—just room! Can you do it, Green?"

As he spoke they were right on the spot where the bomb had exploded. As Derry had said, half the road was gone. Yes, more than half. There was a hole big enough to bury the car and every thing in it.

"It'll be a tight fit," he said hoarsely. "I'll have to shove her up the bank to the left there. Hold on, everyone!"

The near-side wheels rose against the bank, the big car tilted heavily, while the off wheels were right against the crumbling edges of the chasm. For a moment it was nip and tuck, just a chance whether she got through or turned over into the pit. If Green's nerve had failed it would have been all up.

But Green, a trained airman, had nerves of iron. He guided the groaning, roaring car with hands as firm as steel. Earth and stones rattled into the pit, then the car bumped back into the road and safety.

He pointed as he spoke to the airship, which for the moment, and in the excitement, they had all forgotten. She had shot on ahead, but now was coming round again in a wide circle.

Green put his foot hard on the petrol pedal, the engine roared, and the whole car quivered as she struggled up the steepest of the slope. She was now only about a hundred yards from the top.

But the airship had the legs of her. Before she could reach the summit, the ugly white glare of the searchlight fell upon them again.

Once more the thundering engines ceased, but the car still lay bathed in the broad circle of intense light.

"You'll not trick me a second time," cried the pirate, "and if you try it, I'll wipe you all out!"

CHAPTER VI. — THE PIRATE TRIES AGAIN

"BLUFF! Just bluff!" said Derry. "We're safe enough so long as we have the prisoners. Ha! He's off again! Means to catch us on the slope."

"No; he'll drop one on the top of the hill," returned Ned. "See, he's coming right down. Oh, you would, would you?" he continued. "But wait; I'll spoil your game."

As he spoke he hauled out his pistol, and let fly half-a-dozen shots as fast as he could pull trigger at the pirate craft. At the moment she was hardly more than three hundred feet up, and at such a range every bullet told. Every one at least hit her somewhere.

The echoes of the shots had not died before there was another whizz and a second terrific explosion. This bomb burst just out of sight, over the crest of the hill, and the back lash of the explosion was not so great as that of the first. No one spoke. The suspense was too great. They waited until the groaning car had topped the rise; then Ned gave a yell of delight.

Sure enough, this second bomb had missed the road altogether, exploding harmlessly on the open moor quite twenty yards to the left.

"Yes, you spoilt his aim," replied Derry, with delight. "Now, then, Green, all clear. Let her go."

Green merely nodded as he changed up swiftly from first to second, and then from second to third. The car fairly leaped forward. Another moment and she was on top gear, and flying like a scared cat down the long, winding descent.

"But we are not done with our pirate friend yet," said Mr. Murston, in his deep voice. "See, he is chasing us."

"He's got something to chase while Green is at the wheel," replied Derry. "I don't think he could hit us even if he tried. A car's a small object from the air, and even if he tries the road again he can't slow down to make sure of his aim."

"That is true, Holt," agreed Mr. Murston. "At the same time our persecutor is a person of resource, and I do not think he will accept defeat without a strong attempt to avert it."

"There are trees in the distance," put in Ned. "We shall be all right when we reach them."

"Yes, and if I remember right, the rest of the road runs through woods," Mr. Murston told him. "But we have to reach the woods first, and there are a couple of miles or more to go still."

The great car lurched horribly as he swung her round curve after curve, and Derry's breath came quickly as he saw the perilous turns pass one after another.

It was the sort of hill that, ordinarily, a driver would have taken on second speed and with all brakes on. As it was, Green had not even cut out his engine, let alone put over his brake levers. The pace was appalling, and the cold air fairly shrieked past their ears as the car fled downwards.

Upon the open moor the wind had almost cleared away the snow, but here the road ran between high banks, and was covered several inches deep. Here and there they struck little drifts, which were hurled into dust before the rushing wheels.

The nearer they got towards the foot of the hill the deeper these drifts became, yet Green chanced them, for the dirigible was still ahead. They were going as fast as she, but while they had to keep to the curving road, the pirate was able to drive straight ahead.

What his next move would be they could not tell, but it seemed certain that he would shortly try to put another bomb in front of them.

At the mad speed at which the car was travelling the bottom of the long hill grew rapidly nearer. Green took the last curve on two wheels, and the big acetylene head lights showed a long straight stretch extending clear down to the flat country below.

They showed something else—a drift as high as the bonnet, a great bar of snow lying clean across the road.

"Chance it." said Derry. He turned in his seat. "Hang on tight," he bade them sharply.

Next instant the big car hit the drift. It was like a snow plough on the line. Great chunks of snow flew high on every side. The jar was fearful, and if they had not been holding on like grim death, everyone would have been shot out.

The car checked, but only for an instant; her wheels skidded, then gripped again. With a convulsive heave she cleared the last of it, and at a somewhat slackened pace ploughed on through the shallower stuff beyond.

"Heaven send she ain't damaged," breathed Green. "'Twas enough to knock the very stuffing out of her."

"There's something amiss," said Green grimly. "If I'm not mistook, a tyre's gone."

"You're right. It's the near front tyre. But you can't stop till you reach the trees. You'll have to drive her on the rim."

"Still almost overhead. But a bit higher than he was. He doesn't like that pistol of Mr. Barlow's."

"If he puts another bomb down we're done," added Green. "There's no getting off of a road like this, with big banks both sides."

"Tyre gone, sir," replied Green; "but we haven't got no time to change it yet. We'll wait till we get to them woods."

The wood was plainly visible, black against the snow-clad landscape, and not more than a mile away. But it was, of course, impossible for Green to drive as fast as before, and now the pirate dirigible had shot some way in front. Every moment Derry expected to hear the thin whistle of a falling bomb. His eyes were fixed upon the threatening shape which blotted out the stars.

"If he gives us another three minutes, we'll be safe," he said to Green. "He won't see us once we're under those trees."

"Not if we switches the lights off," replied Green; "but it's my belief as he's just waiting, a-playing with us like a cat with a mouse."

Derry felt a cold shiver down his spine. The idea was simply detestable, yet only too likely to be true.

The pirate was coming lower again, and his long craft bulked larger as he descended. But now he was too far ahead for Ned's pistol to be of use.

Lower and lower, till he seemed to be almost touching the tops of the trees in the wood just beyond.

But this time, though he strained his ears, he could hear no sound of anything falling. What he did see was the dirigible turning at a sharp angle away from the road.

"He may be, but I'll lay he's up to some trick," replied Green; and to Derry's surprise he cut off gas, checking the speed of the car.

It was nothing but that which saved them. Next moment the road just ahead burst into flames. They roared up in blue tongues. It was a veritable lake of fire.

Green clapped on both brakes, and did it just in time. The front wheels were so close to the flames that the heat of them almost scorched their faces.

"Aye, or paraffin, and with a time fuse. Boss, we're done in!" said Green. "See, he's coming down after us."

"No room to turn, sir," replied the mechanic. "I don't want you to turn. We must rush it."

"Why not? Even with that burst tyre you can do thirty. We'll be through it like a flash."

Green glanced at the bellowing blue flames. They had licked up the snow; the wet grass and the hedges themselves were burning. Then he turned to Derry, and there was a gleam in his keen eyes.

"Not in the least. I would do more to get the better of our friend, the sky pirate."

Green backed out. The dirigible was so close that they could see every detail of her in the glare of the flames.

"Cover up your faces, gents," sang out Green, and without another word sent the car flying forward.

Derry held his breath as they rushed at the sea of flames. They filled the narrow road from one side to the other, and stretched out on a width of twenty yards or more. It was a regular burning fiery furnace, and it seemed impossible that they could ever get through alive.

The heat was frightful. Derry felt as if the skin were peeling off his face. He caught the harsh smell of blistered paint and burning hair.

The ordeal seemed to last whole minutes. As a matter of fact the passage took less than three seconds. Then they were through and the car tearing onwards into the darkness beyond.

Derry opened his mouth, and took a long gulp of the frosty air. He glanced round at Green's face and saw it black as a sweep's.

"We've done it. Splendid!" cried Ned, from behind. "Now for the wood and safety!"

Green said nothing. Gripping the wheel with blistered hands he kept the car going for all she was worth, and three minutes later they shot in under the welcome cover of the trees, where he switched off the lights.

"Now I reckon we've diddled him," he remarked, and, bringing the car to a standstill, got out and began to unstrap the spare wheel from its frame.

"Not much, Green," said the former. "You've done your job. This is ours." And pushing him aside, the pair set to work to jack up the car and change the damaged wheel.

Mr. Murston, too, got out, and walked away a little into a more open space, from which he surveyed the sky.

"He's gone," he said, in his deep, rolling voice. "Gone home, if he has one, and given us up for this night. My friends, I am very pleased with you, and very grateful for all that you have done for me to-night. Green, you are a driver after my own heart. I would like to tempt you to leave your young employers and become my own chauffeur."

"I did not suppose there was, and I should have thought less of you if there had been. But you will not, I suppose, object to accepting a small present from me in return for your services."

Green glanced at it by the light of the small lamp the boys were using. He looked rather scared.

"You made a bloomer, sir," he said, offering it back. "This here's a note for a hundred quid." Mr. Murston smiled.

"I know that, my friend. Surely you would not have me value my safety at any less rate." Mr. Murston turned to the boys.

"You two have lost your airship in my service," he said. "How long will it take you to build a new one?"

"I didn't ask you what it would cost. I asked you how long it would take to build."

"Then do it," was Mr. Murston's reply. "I'll foot the bill. And when you have done it—then—then I'll tell you what to do with it."

CHAPTER VII. — THE MAN IN BLUE

THE rest of the journey was perfectly peaceful. The pirate and his ship and his bombs might have vanished into thin air for anything that Derry and his party could see of them.

As for Derry himself, he was so excited about Mr. Murston's amazing offer that he could hardly think of anything else. To be allowed—indeed, ordered—to build a new airship regardless of expense seemed too good to be true.

It was Mr. Murston's voice that broke upon his dream, and, looking up, he saw a row of lighted windows on the slope opposite, and only a few hundred yards away.

"They haven't all gone to bed," chuckled Mr. Murston. "They knew I'd come. I've never disappointed them yet, though I've had some close shaves even before this. Holt, never be a millionaire. It's too wearing."

"This is it. Healthiest place in England, and one of the prettiest. The youngsters love it. Through the gate to the left, Green! That's it! There's a garage round at the back, and when you've put the car away, come in and tell me, and I'll show you where we can stow our prisoners for the night. Oh! and remember this, please," he added, "not a word of the attack to Mrs. Marrable or the nurses. No use scaring them. I'll tell them we came by airship part of the way, and the rest by car."

The building was a large and handsome one. Derry could see that much. Before he could take in anything more, the front door was flung open and a lady in nurse's uniform came hurrying out.

"Better late than never, Mr. Murston!" she exclaimed delightedly. "Some of them vowed that you would not come—that the railway strike would make it impossible, but I knew you would be here before morning."

"It was a tight fit this time, Mrs. Marrable," replied Mr. Murston genially. "If it had not been for these boys I should never have done it. They brought me most of the way by airship. Let me introduce you! Mr. Derry Holt and Mr. Ned Barlow, Mrs. Marrable."

He hustled them in, leaving Green to take the car and the prisoners round to the back.

The boys found themselves in a large, well lighted hall. It was deliciously warm, too. Everything was decorated with holly and mistletoe, and had the brightest, cheeriest look.

"I am greatly indebted to you, Mr. Holt and Mr. Barlow," said Mrs. Marrable, a handsome, pleasant-faced woman of forty. "You can't think how we look forward to Mr. Murston's Christmas visit, and so do the children. They all love him, and they ought to, for he has taken them from miserable homes, or no homes at all, and is giving them their chance in the world. But you are frozen, you poor things," she continued, "and I am sure you are frightfully hungry. I will show you to your rooms, and supper is quite ready and waiting."

If their arrival had been arranged a week ahead, the rooms could not have been nicer. Hot water was ready, fires were burning—all was cosy as possible.

They tidied themselves up as best they could, and hurried down to supper, which was ready in the matron's dining-room. It was a meal such as Derry and Ned had not seen for months.

Hard up as they had been, they had been living very much on the rough side for the past six months. Here were hot soup, cold chicken, ham, a delicious trifle, and a cup of excellent hot coffee to top up with.

Mr. Murston, who was clearly delighted to have reached his destination safely, talked sixteen to the dozen, and kept everyone amused.

In spite of the late hour, they sat a long time over the cheery meal. They were just getting up when there was a ring at the hell.

Derry went out. Opening the door, he found a policeman on the steps. A young man, rather tall, and smarter looking than the average run of rural constabulary.

"I am from Greeba, sir. I am in charge there. About an hour ago a man came in to say that he had seen and heard two heavy explosions on Greeba Fell, and that he thought it was an airship attacking a car. I called up Donthorpe, and got word that a car had been seen by a gamekeeper coming from that direction through Scranton Woods, so I got out my motor-bicycle and followed. I found your tracks in the snow, and came on here to Shorn Fell, and learnt that you had come to the Orphanage. I thought you could tell me what was up."

"Come inside," he invited, "and take a seat. I will tell Mr. Murston, and he will speak to you."

"It's someone to see you, Mr. Murston," he said quietly. "About that little accident," he added, significantly.

"Right, Holt. I'll come. It's all right, Mrs. Marrable, just a question of compensation."

"It's a policeman," Derry began, as soon as Mr. Murston was outside the room and the door closed. "He's heard of the bombing business."

"The law is not such an ass as some people think," remarked Mr. Murston. "All right, Holt. I'll interview him. You'd better come, too."

"I suppose I had better, though I must say I should have preferred to keep it quiet."

"But there are the prisoners!" objected Derry. "So there are, by Jove! I'd forgotten them for the moment. Well, I shall be just as pleased to get rid of the responsibility of keeping them."

The policeman had his notebook ready, and rapidly jotted down the information which Mr. Murston gave him.

"Rumours, sir, but I must say I hardly believed them. It seems almost beyond belief that a man should have the impudence to try such a thing, especially with a great craft of this sort. I don't see how he can hope to hide a thing like that."

"I suppose I had better, sir," replied the policeman, a little doubtfully. "But I don't think I can take them back to Greeba to- night. There's no getting any conveyance."

"I'm not much of a hand at it, though I can manage a motor- bicycle. Are they safe where they are, sir?"

"Very well, sir. I'll see them now and find whether they have any statement to make, but I think, if you will allow me, I will leave them there until morning."

The prisoners were not in the wash-house itself, but in the boiler room adjoining. They had been put there because the place was warm. In any other outbuilding they would have probably been frozen stiff by morning.

Green had not been taking any risks, and both men were handcuffed. They were drowsing in two chairs, looking very sullen and uncomfortable.

"They've no call to complain, sir," explained Green, coming in. "They've had some grub."

"You'll have to tell them when you're brought before the Bench," said the policeman severely. He asked several other questions, but got very scant replies.

"They won't talk, sir," he remarked at last, turning to Mr. Murston. "But, after all, that doesn't matter. And now, if you please, I'll leave and get back. I shall call for them with a car and a driver at nine to-morrow morning, if that will suit you?"

"All right," replied Mr. Murston. "They should be safe enough here for the night."

"Perfectly safe, sir!" said the other, respectfully. "Good- night, sir!" And, saluting, he went out.

"A smart fellow!" nodded Mr. Murston, approvingly. "And now let us all go to bed. I'm sure we need a good sleep after the experiences of the past few hours."

They returned to the house, and half an hour later all lights were out and every one of them peacefully asleep.

CHAPTER VIII. — THE NEW ENGINE

He opened his eyes and looked round. The room was full of the cold, clear sunshine of a perfect winter morning, but Derry was still only half awake, and for the moment could not remember in the least where he was or how he came to be in this unfamiliar room.

Recollection came back to Derry all in a flash, and he leapt out of bed, ran to the door, and flung it open.

There was Green thumping with his fist on the door of the room opposite. As Derry came out the other door was thrown open, and Mr. Murston's portly form appeared, wrapped in a thick, fleecy dressing-gown.

"What is it, Green?" he demanded, in his deep voice. Though he had evidently only just roused out of sound sleep, he showed no sign of annoyance.

"The prisoners gone?" repeated the other, yet without changing his tone in the least.

"Yes, sir!" answered Green, who was plainly much upset. "The door has been unlocked from outside. Someone has let them out."

"My good Green, I am quite sure of that. But pray, do not get excited. No, I do not think there is any need for me to come down. It is very cold, and I can take your word for what has happened."

"Ah, Holt, you are younger than I! Will you go down and investigate? I really need a little more sleep. The fact is that I have only just got to bed. I have been round the dormitories distributing my little gifts to the children."

He flung on his clothes, and followed Green down to the wash- house. Sure enough, the door was open and the birds had flown.

"That's how I found it when I came down," said Green. "It's too bad, sir! I wouldn't have had it happen for all the money the gent gave me last night. I'd ought to have sat up and watched, only the policeman said it was all safe, and Mr. Murston himself, he told me to go to bed."

"You're not to blame, anyhow," Derry comforted him, "but who on earth could have let them out?"

"I can't imagine, sir, unless the pirate chap followed us without our knowing it."

"It seems to me that is just what must have happened," agreed Derry. "We were flats not to have thought of it."

"But how could he have known just where they were locked up, sir?" demanded Green. "He couldn't possibly have been near enough to see. And it's a big place, this, with a lot of outbuildings."

"Nothing of that sort. You see, it was freezing all night. You couldn't even find our footprints where we came in last night."

"Let's go inside and have a look round," suggested Derry, and went into the room.

A folded sheet of paper lay upon a shelf just above the two empty chairs. Derry took it, smoothed it out, and ran his eye through the few lines that were pencilled on it.

"Of all the cheek!" he cried angrily, then broke off into a rueful laugh. "Oh, Green," he said, "it's our own fault. Listen to this—

"'I told you that I would call for the prisoners. I have done do. Since they seemed to find the air here a trifle enervating, I have removed them to higher altitudes. Pleased to do the same for you a little later.—Yours, James Spain.

"And I was fool enough to let him take me in like that. Oh, jiminy! I could kick myself from here to London!"

"He took us all in," he said, "Mr. Murston included. So you need not feel too bad about it, Green."

"Oh, but I do, sir! To think of being fooled like that! Why, the chap was in our hands, so to speak!"

"He was jolly well disguised, anyhow," said Derry. "Now, don't worry, Green. The thing is done, and can't be helped, but we shall be wiser next time."

"We'll never have another chance like that," groaned Green, and leaving him still lamenting, Derry went into the house to tell Mr. Murston and Ned.

"I'm not so sorry," he said. "I like publicity, but not that sort. It's too much like the actress who gets her jewels stolen as an advertisement. I don't want to see headlines in the newspapers: 'Air pirate bombs Mr. Mark Murston. Another ad. for Arkles, Ltd.'"

"Well, you know now. I suppose you thought that I was kidding you last night when I told you to build a new airship?"

"You won't be astonished any more. In a day or two you can start to get out your plans and specifications. For the present you and Barlow are to have a holiday."

Though having a jolly time, Derry's mind was busy with his new airship, and he and Ned constantly talked over their plans.

"I've got Dad's drawings," Derry told Ned. "You know his great idea was a turbine engine. I believe it can be done. I'm going to ask Mr. Murston about it."

"You must get those plans worked out," he said, "but to the best of my belief there is only one firm in the world that can work them. That is Braddock's, of Syracuse, New York State. I know Braddock well, and he will do anything for me." He paused. "Look here, can Green be trusted to collect the material for the new craft?"

"Very well. Then you and Barlow had best go over to America at once and get this engine put in hand. You can be back with it in about six weeks."

He made his preparations as quickly as possible, and, leaving Green to get the material ready for the ship, he and Ned sailed three days later for New York in the Mauretania.

The mere mention of Mr. Murston's name worked wonders. The two friends were treated almost royally on the great ship, and once they were in the States everything possible was done for them.

Mr. Randolph Braddock, head of the firm, was all that Mr. Murston had described him. He was a most brilliant engineer, and from the moment he had looked through Mr. Holt's plans was as keen as Derry himself.

"I guess it's just what I've been trying for these five years past," he said. "You'll get double the power with half the weight. Say, but this is going to be some engine, Holt! I've got the special steel, and I'll start in right away. I reckon to have it finished inside four weeks' working time."

He was as good as his word, and within a month Derry was able to cable to his employer:

The two packing-cases containing the new engine were sent down from the works under special escort, and Derry himself saw them stowed safely in the hold of the giant liner.

Punctual to time, the big ship left New York harbour, and steaming past the tall Statue of Liberty, drove out to sea at twenty-five knots.

The first three days were rough, but after that the weather improved, and the fourth broke with a glorious sun, a smooth sea, and a warmth which for February was quite startling.

"Only four hundred miles from the Irish coast," said Ned to Derry, as the two stood together on the upper deck watching the clear, green water swirl past the tall sides of the rushing ship. "We shall be in Liverpool to-morrow night."

"I'm counting the hours," Derry answered, with a smile. "I shan't be happy till I've got the new engine into the new ship. I tell you, Ned, she's going to startle people. If my plans work out, I believe we shall have a dirigible that will do over a hundred in still air. I'm going to build her of steel on that new central tension plan, and on the lines that Dad used to talk about so much. Then we'll fill her with helium gas instead of hydrogen, and I'll defy our pirate friend to fire her as he did the old one."

A stir on the deck behind made him look round. People were hurrying up from below.

"They're all craning their necks in the air." said Derry, as he, too, stared up. "Hullo, it's a dirigible. A big one, too. One of our R class, I suppose."

Ned produced a pair of field-glasses from a case slung over his shoulder, and proceeded to focus them.

"No," he said presently. "She's not one of the old R's. She's slimmer, and a bit different in shape. Tell you what, Derry, she reminds me of that pirate craft, only she's a lot bigger."

"You're right, Ned. The lines are just the same. But surely even James Spain, as he calls himself, would hardly dare to hold up a liner on the high seas?"

By this time there were several hundred passengers on the upper deck watching the dirigible, which was fast growing in size as she came nearer. She was coming up aft, and travelling quite three times as fast as the ship.

Derry had the glasses now. He was standing as still as a statue, watching with all his eyes. Suddenly he lowered the glasses.

"Ned," he said quietly. "I believe you are right. I believe that is the pirate himself."

CHAPTER IX. — HELD UP!

"WE must tell the skipper at once," said Ned, darting away towards the bridge, closely followed by Derry.

But the crowd was thick, and by the time they had elbowed their way through it, the great airship was within a mile of the liner. She was coming down fast. When they had first sighted her, she had been at least three thousand feet up, but now was hardly more than three hundred.

As the two boys reached the foot of the bridge ladder, the skipper was already staring upwards at the dirigible with a decidedly puzzled expression.

"I must see the captain at once," returned Derry, and there was that in his voice and manner which made the man give way.

"I must speak to you a moment, Captain Strahan," said Derry in a low voice. "It's about that airship."

"It's this, sir. Barlow and I think that the airship belongs to James Spain, the air pirate, of whom you may have heard."

"The air pirate!" repeated the captain in amazement. "Oh, you mean the man who held up the Borussia last year?"

"He's done other things of the same sort, sir," said Derry. "He held up Mr. Murston, of Arkles', no longer ago than last Christmas."

"I don't see it, sir. Big as the Leviathan is, he could sink or set fire to her just as easily as he did in the case of the Borussia. Look at him! He is almost over us."

He was right. The great dirigible was almost overhead, bulking huge against the blue sky. She was two-thirds as long as the Leviathan herself, and so near that they could see every detail of her, while the roar of her powerful engines was almost deafening.

Suddenly the engine roar slackened, or rather was decreased greatly in volume. At the same time the speed of the airship decreased.

"He's cut out two of his three engines." exclaimed Ned Barlow. "Now look out for squalls."

"Bates, go at once to Mr. Meares, and tell him to be ready to send out an S.O.S. the moment he gets orders. If anything happens he is not to wait for orders, but to do it at once."

All this time the airship was dropping slowly, until she was almost level with the Leviathan's mast-head and perhaps two hundred yards away.

Then, without any warning, the air was rent by a sudden crackle of firing, and overhead a storm of bullets whined and sang.

"He's not firing at us, sir," put in Derry quickly. "It's at the aerial. See, he's shot it away."

"You are right. And that lands us. Still, I don't see how he's going to stop us."

"Then I'm afraid it's all up, sir," replied Derry. "He's got bombs of all kinds."

As Derry spoke, the remaining engine of the airship ceased working and in the silence which followed a voice—a voice whose thin, high, piercing quality Derry remembered only too clearly—came down from above.

"Hard aport!" he said curtly to the man at the wheel, and at the same time shoved over the engine-room telegraph to full speed.

The great ship seemed to leap forward, and at the same time swung away to port leaving the airship drifting to starboard in the light breeze.

But almost instantly the latter's engines all roared out again, her nose swung round, and without any effort she came right over the liner. Speeding forward, she turned slightly, and crossed the bows of the Leviathan. As she did so, a small dark object dropped from her 'midship gondola.

Derry saw it, but before he could open his mouth it had struck the water not half the ship's length ahead of her and exploded. What horrible stuff it was filled with Derry could not tell, but the roar of its bursting made the whole great ship shiver as though she had struck a sand-bank, while a column of foam shot up at least fifty feet into the air.

"That settles it," said the skipper, between set teeth. "I have my passengers to think of."

As he spoke, he rang off the engines, and next minute the great ship floated quietly as a log on the slow Atlantic swells.

"I thought you'd see reason," came the pirate's thin, harsh voice. "No more monkey business, if you please, or I shall use my machine guns."

"A little more moderate language in the first place," was the sarcastic answer. "In the second, that you lower a boat."

Derry saw big drops of perspiration stand out on the skipper's forehead. He knew how desperately he must feel the helplessness of his position. Yet with the better part of two thousand human lives to answer for, he could do nothing but submit.

A boat was lowered. It had hardly touched the water before a figure left the airship and came shooting downwards. The watchers on the deck saw a parachute open, and the man came swinging down gently into the sea, falling barely fifty yards from the ship. He wore a sort of swimming dress, which kept him afloat until the boat picked him up.

The boat came alongside, with Spain's agent aboard. He was a tall, finely-built man, not by any means bad looking, but with a jutting chin, a hooked nose, and dark eyes burning sombrely under heavy brows. He was dressed in plain dark blue, a kit that strongly resembled ordinary naval uniform, only that the facings and rings were black instead of gold.

Without a glance at any of the silent folk who stood on the deck, he marched straight up on to the bridge, where Captain Strahan was standing.

"Captain Spain's compliments, sir! He is sorry to inconvenience you, but you have cargo aboard which he requires. They are two cases addressed to Mr. Mark Murston. He asks you to give these up at once, and will then trouble you no further."

"He is kind, indeed," he retorted. "As I am unarmed, I have no choice but to obey."

Derry, who was still on the bridge, had heard the pirate's demand. He stood for a moment unable to speak. Then suddenly he sprang forward.

"They are ours, captain," he cried. "They contain the engines of our new airship. If you give them up, you make this pirate ten times as dangerous."

"I am sorry, Mr. Holt," he said gravely, "but with two thousand lives and some two million pounds' worth of property under my care, I have no choice. You can see that for yourself. The company will pay Mr. Murston compensation."

"It is not a question of compensation," returned Derry vigorously. "This man Spain must have had us watched. He knows that this engine is the only thing of its kind in the world, and he means to seize it for his own use. If he succeeds, the results may be terrible. They will be terrible."

"Whatever the results, they will hardly be as bad as the sinking of the Leviathan with every soul aboard her. Kindly make up your mind quickly, Captain Strahan. We have no time to waste."

"If I had only myself to think of, I would tell this murdering scoundrel above to go ahead. At any rate, you would go down with us."

"I should," replied the other calmly. "Still, that would not do you much good. As I have said before, you must kindly make up your mind at once."

"I must comply, Mr. Holt," he said, quietly. "Much as I regret the necessity, there is no help for it."

Derry was nearly frantic at the idea of losing his treasured engine. Yet even he could see that there was no alternative.

"Nothing," replied Derry. "It's the ship or our engine. Don't talk to me, Ned. I can't stand it."

Ned himself was almost bursting with rage. Though the new engine was from Derry's plans, not his, he had watched every bit of it made and put together, and was as keen on it as Derry himself. To lose it was bad enough, but to think of it in the hands of the pirate ruffian was a thousand times worse.

One thing that he and Derry had been hugging themselves over was the thought that with the new engines they would have the legs of any other dirigible in the world, and would be able to make rings round Mr. James Spain if he ever tackled them again.

Now the pirate would have the whip hand of them and of everybody else. His power for mischief would be enormously increased.

Meantime, Spain's swarthy lieutenant was issuing orders as if he owned the ship. The forward cargo hatch was raised, and under his direction men were busy with a derrick and the donkey engine. Ned, watching, saw that the man knew exactly where the cases had been stored. Quite clearly their storage had been watched by Spain's spies.

Under the threat of the great airship, which, with her engines moving slowly, hung directly over the big liner, the work proceeded quickly, and within a very few minutes Ned saw the two familiar cases lifted up out of the hold and dropped gently on the deck. By Spain's lieutenant's orders they were slung over into the boat which lay alongside; then the lieutenant and four men got aboard the boat and pushed off. When at a respectable distance from the ship the pirate craft dropped lower until she hung no more than fifty feet above the sea.

Slings were lowered from her central gondola; then came one of the cleverest bits of handling which Ned or any of them had ever seen, for while the cases in turn were being hauled up the big airship kept her position and balance perfectly. It was clear that fresh gas was being let into her containers, while at the same time water ballast was being released in a measure just sufficient to balance the extra weight.

The cases were slung aboard the pirate. She was drawing up her man, when Derry felt a touch on the shoulder, and, glancing round, saw Meares, the wireless operator, standing beside him.

"What do you mean?" demanded Derry. "It's all over. Spain has got my engines. See! He is already under way."

"I know that. Luckily, I have a second string that no one else knows of." He bent over and whispered in Derry's ear. "It's a wireless telephone with a separate aerial. Precious few ships have it yet, except warships. So I hardly expected an answer. But by a wonderful stroke of luck I've got one. It's from the Ark, the seaplane ship. She has launched a seaplane. Ah, here she is already!"

CHAPTER X. — THE COMING OF THE SEAPLANE

MEARES was right. Far on the horizon, so small that it took good eyes to see her at all, a dark speck was visible against the blue of the sky, and Derry's heart leapt at sight of it.

Ned was as delighted as Derry, and the two stood watching the little dot in the sky with hearts pounding from excitement.

There was no doubt about it. Spain had spotted the 'plane, and the pace at which his black-browed lieutenant was swung up to the car must have been a bit trying to that gentleman's feelings.

Even before he was in the car the pirate craft was rising. The passengers in the Leviathan craned their necks as the long, cigar-shaped hull dwindled into the blue above.

Derry and Ned were nearly wild with excitement. There was no way of communicating with the seaplane, which was still three or four miles away. Her crew could not know what was up. They would have to come alongside the Leviathan in order to be told.

There was nothing for it but to wait, and the next four minutes were like a year. Every moment saw the pirate craft dwindle in size as—with all her engines working at top speed—she fled to the northwards.

"The sky's clear," he said, "and the 'plane can probably do twenty an hour better than Spain's ship. Even if she gets fifteen or twenty minutes' start, she ought to overhaul her within an hour. And I'm pretty sure we shall follow to pick them up in case they run out of petrol. Ah," he went on, "here she is. My word, but she's been moving like smoke!"

Almost before he had finished speaking the seaplane came swooping down to drop within easy distance of the liner.

A naval lieutenant muffled to the ears stood up in the boat- like body of the craft.

"That dirigible has held us up and stolen cargo," shouted back Captain Strahan. "We want you to overhaul her."

The captain, turning, saw Deny, and paused. "Can I go, sir?" begged Derry. "I can explain."

"All right," came the answer. "Plenty of room. But be sharp, or we shall lose her."

The boat which the pirate had used had not yet been hoisted in. Derry grasped a rope and went hand over hand down it like a monkey. The moment he was aboard the crew gave way, and in less time than it takes to tell Derry was on the 'plane.

The seaplane engines roared, and, rushing forward, she took off like a sea bird from the top of one of the long, slow swells, and went rushing upwards at a steep slant.

Derry, crouched behind the pilot in the tiny cockpit, looked back and saw that they were already high above the mast-heads of the liner. He waved his cap, and even above the clatter of the 'plane's exhaust heard a deep thunder of cheering.

He glanced ahead. The pirate, looking like a silver cigar slung against the sky, was still visible. He leant over and spoke in the pilot's ear.

"We're on her track, anyhow," answered the other confidently. "So long as the weather holds we're all right. That's the only thing that can upset our apple cart."

Derry's eyes roved around the horizon. In the extreme north- east lay a low bank of cloud; otherwise the sky was clear.

"That's it," said the lieutenant, briefly. "It may be fog or it may not. Everything depends on that."

The roar of the seaplane's double engines was deafening; but her pilot, the tall lieutenant, had a telephone receiver fixed over his ears, and by the aid of this and a second receiver he and Derry were able to talk easily.

"You're Holt," said the lieutenant, "aren't you? My name is Hamlyn. Are those your engines which this fellow has gone off with?"

In a few brief sentences Derry told him the story of the new engine, how it had been built in America and shipped in the Leviathan. He explained how Spain had held them up and seized the cases.

"Pretty good cheek!" remarked Hamlyn coolly. "I've heard rumours already of this pirate person, but I can't say I took much notice of them. But I've always said that, once the day of aircraft really began, we should get this sort of thing." He paused with his eyes fixed upon the fleeting form of the big dirigible. "That's a thundering big craft the fellow's got," he finished, "and fast, too. I wonder where his base is?"

"Somewhere up in the Scottish mountains, I should think, from the direction he is taking," replied Derry. "He's running north- east now. Do you think you can catch him, Mr. Hamlyn?"

"We are picking him up already," replied Hamlyn calmly. "But he has a long start, and, of course, he carries a lot more petrol than we do."

"Yes. Don't worry about that. We can keep going for three or four hours, and if we run short, there's always the Irish coast."

"The Irish coast," repeated Derry sharply. "I'm not thinking of our safety, but of catching that scoundrel who's got my engine."

"I know. I was only pulling your leg! Seriously, I believe we can overhaul him. The only thing that really worries me is the weather. We're getting near that cloud fast, and there's a lot of it."

Derry looked. Sure enough, the cloud which, when they started, had been a mere rim along the horizon, had grown so that now it was a deep, dark bank all across the north.

"Yes, it's fog; but it's still a good bit away, and at the present moment we are doing just on ninety-five. We're overhauling him all right."

They were. Derry could see that. The long, slim shape of Spain's airship was much more distinct than it had been, and was growing more so every minute. No doubt Spain was pushing her for all she was worth, but it was hardly likely that she would do more than seventy-five.

There was silence a while. Derry's eyes were fixed upon the pirate craft. Though they were gaining on her steadily, she was getting rapidly nearer to the fog bank. It was going to be nip and tuck whether they caught her before she could reach it.

The seaplane (J19 was her number) had a crew of three, including Lieut. Hamlyn. She was going all out, and the roar of her two great engines was almost stunning. Presently Derry became aware that one of the two other men, a square-built warrant officer, was busy with the machine-gun. The cover was already off and he was getting out trays of ammunition.

The man pointed to the cartridges, and Derry saw that they were Pomeroy bullets, the same that brought down so many German Zeppelins in flames. He turned to Hamlyn.

"I'm afraid we can't help that, my son," replied Hamlyn. "Perhaps Spain will see reason and throw in his hand; we must hope so."

"I don't suppose he will," groaned Derry, feeling very anxious again. It seemed to him that, whatever happened, his beloved engine was lost to him.

"Don't worry," he said. "You can get a new engine built, and once Spain and his crew are out of the way there'll be no one to interfere with you. I say," he added, "we're picking him up."

The 'plane, indeed, was no more than a couple of miles behind the dirigible. Beneath was empty sea. The Leviathan had long ago vanished beyond the southern horizon, and here they were quite out of the ordinary track of ships, with nothing in sight.

All the northern sky and sea were now hidden by a dense mass of grey vapour, and it was for this that Spain was driving for all he was worth.

Derry could hardly breathe for sheer suspense. He sat as still as a statue, his eyes fixed on the big dirigible. She had been flying at a great height. Now she was dropping in a long slant. Spain's idea was evidently to drive into the thickest of the mist, which was, of course, that part nearest the sea. A sea fog is rarely more than half a mile deep.

The 'plane raced after her like a wide-winged hawk chasing a great carrion bird. She was picking up a mile in every three minutes, and the hopes of all in the 'plane rose high. It began to be certain that they would overtake their quarry before she could reach the fog bank.

"We've got her," said Hamlyn quietly. "It's going to be a close thing, but we ought to be within shooting distance just before she slops into that smother."

As he spoke he was busy with his controls. J19 began to rise in order to get above the airship. This manoeuvre lost her a little distance, but even so she seemed to have the pirate craft at her mercy. The latter was still a couple of miles from the slow-moving fog bank, while the seaplane was almost within gunshot of her.

Another minute passed; then Hamlyn turned his head and made a sign to the man at the gun. The latter at once proceeded to train the sights of his Lewis gun upon the long, cigar-shaped form, now almost beneath them.

Before he could fire a shot the outlines of the pirate craft suddenly dimmed, then with a swiftness that was almost miraculous faded from view. In a moment the fog seemed all around her.

As Bullock pressed the trigger, the crackle of the machine-gun mingled with the thunder of the engines, and a stream of bullets tore across the gap between the 'plane and the dark cloud, which was all they could see of Spain's craft.

"He's made a smoke-cloud," answered Hamlyn curtly. "It's the old Hun dodge. Holt, I am afraid he has done us, unless we can get in a lucky shot and fire him."

Next instant J19 was in the cloud. It was an acrid, eye- stinging vapour, white as fog but even thicker.

"Chloro-sulphonic," Derry heard Hamlyn say. "I can tell by the niff of it. He's driven it out through his exhaust. Where the mischief has he got to?" he growled. "Can you see him?"

But Derry couldn't. His eyes were streaming, and he felt half- choked by the reek. It lasted only a minute, then they were out on the far side. Hamlyn banked and came round.

Hamlyn looked up. More than a thousand feet above them, and rising like a bubble, was Spain's ship.

All the same he sent his big machine wheeling up in circles in pursuit. But a plane cannot rise like a dirigible, and long before J19 got her height the pirate had shot into the vast fog bank and was lost to view.

For another hour they hunted her, but it was useless. Then they turned eastwards and made for the Irish coast.

CHAPTER XI. — WELCOME NEWS

DERRY reached London via Galway, Dublin, and Holyhead just at the same hour that the Leviathan berthed at Liverpool, and at once telephoned Mr. Murston at his office.

"I've heard," was the answer. "No, we won't talk over the wire. Take a taxi and come here."

Fifteen minutes later the taxi drew up in front of the enormous pile of buildings, along the front of which was blazoned in gold letters the name of "Arkles, Ltd."

Derry paid the cabman and went straight in. He knew his way. A lift shot him up five storeys, and he tapped at a heavy mahogany door bearing the name of "Mr. Mark Murston."

"Come in," came the deep voice he knew so well, and as he entered the large, quietly-furnished airy room, Mr. Murston rose from his desk chair to greet him.

"About our pirate friend's little stunt?" replied Mr. Murston, still smiling. "Yes, it was cool cheek on his part, holding up the biggest liner in that fashion. But that chase of yours must have been quite interesting. I understand that he got away in the fog."

Derry could find no words. Was it possible that Mr. Murston had not heard of the loss of the engine?

"You're looking thin, Holt," continued his employer. "I think I must take you home to dinner this evening."

"You don't understand, sir. Spain has got away with the engine. I suppose the papers did not mention that?"

"I read that he got two cases out of the Leviathan replied Mr. Murston, as calmly as ever.

"They were the ones containing the engine, sir. He's got them and gone away with them. It's all up. Once he fits his own craft with that engine, he will be able to travel as fast as most 'planes. Even if we get a duplicate from America, Spain will still be as fast as ourselves. We shall be absolutely at his mercy."

"Marks can be duplicated," suggested Mr. Murston. Then he laughed outright. "It's a shame, Holt. I won't keep you in the dark any longer. Spain has risked his neck and roused a regular hornet's nest for the sake of a choice collection of old scrap iron. Incidentally, how I would love to see his face when he opens them!

"You see," he went on "I realised long ago that, in Spain, we had a bold and dangerous adversary. The man is running this pirate business on up-to-date lines. He has his spies all over the place. The more I thought of it, the more certain I felt that he would make some attempt to get hold of this engine in transit. At first I thought of writing to you of my suspicions. Then it occurred to me that I should only be making you nervous and uneasy, and that you might possibly give yourself away. There was a simpler way of doing it. I happen to know one of the directors of the Green Star Line, and it was a perfectly easy matter to get him to arrange that your cases, once aboard, should be duplicated. They, the real ones, were placed in a cabin on the lower deck, while the doubles were stored in the place where you had seen the genuine ones packed. Now do you understand?"

"I suppose it did not occur to you, sir, that it was rather hard luck on Barlow and me?"

"My dear boy, of course I knew that," he said quickly. "But it was necessary. Suppose that you and Barlow had been in the plot, are you both good enough actors to have concealed your feelings? Don't you understand that the very fact of your distress was the best safeguard against Spain or his lieutenant having any suspicion of the real state of affairs?"

"Yes," he said at last. "I suppose you are right, sir. But I haven't had a very happy time of it during the last thirty-six hours."

"I am quite sure you have not," replied Mr. Murston sympathetically, "but I want you to console yourself with the thought that the engine is safe after all, and will be in your works at Marchester by the day after to-morrow.

"Now," he continued, "I want to make up as much as I can for what you have been through. I am going to take you home with me to dine, then we are going to a theatre—that is, if you feel up to it—and to-morrow we are going to have a day's shooting at my place in Surrey. Does that appeal to you, or is there anything else you would like better?"

"It will all be delightful, sir," was Derry's grateful reply, "and I should like it enormously; but I think, if you will allow me, I ought to run straight up to Liverpool to meet Ned, and tell him. He is as worried as I was."

"That's the proper spirit, Holt," said the other with warm appreciation, "but as it happens there is no need for anything of the sort. Your man, Green, is already in Liverpool, and will meet Barlow at the dock and give him a letter from me, explaining everything. I have asked Barlow to come straight up by the night express, and I hope he will be with us, for our day's sport to- morrow."

When they reached the millionaire's house in Park Street, Derry found dress clothes awaiting him in a big and beautifully furnished bedroom. There was a white shirt, patent leather shoes, ties, collars, pyjamas, everything he could possibly need, and all fitting as perfectly as if made for him.

The two dined together at a small table in a most delightful room, with a log fire roaring in the grate. Then the car came round and carried them to the theatre. It was a roaring farce, and Mr. Murston laughed almost more than Derry.

That night Derry slept like a top on his perfect spring mattress, and woke to find a manservant setting a tiny pot of tea and dainty bread and butter beside him.

"Yes, sir, Mr. Barlow is here," the man told him, "but he is still asleep. Breakfast is at nine. Will you take your bath hot or cold?"

"Cold," said Derry as he tumbled out. He had not finished dressing before Ned was in the room, greeting him joyously.

After breakfast a big touring ear appeared, in got the three, and driving quietly through London, quickened their pace when they reached the open country, and by eleven o'clock arrived at Cloam, Mr. Murston's country house, which stood in the middle of fir woods with a great sandy common behind, covered with furze and heather, and swarming with rabbits.

Guns were ready, and a man with ferrets, also guns for both Derry and Ned, and for the next two hours they had wonderful sport. Then came lunch, which was brought out to them from the house, and afterwards they moved to a belt of coppice where wood- pigeons were plentiful.

"That is my boundary," Mr. Murston explained. "The land on the other side belongs to a Mr. Cyprian Coyle. He is rather a queer fish, I believe. Very wealthy and something of a hermit. I am told he is a scientist, and has a large laboratory where he experiments. The country folk are scared of him, and, upon my word, I hardly wonder, for he is the strangest looking person."

Derry and Ned paid little attention to Mr. Murston's information. Neither of them had ever shot pigeons, and they were as keen as mustard to get their first bird.

Mr. Murston showed them where to stand. He put Derry nearest the fence, but still a good way from it; Ned was next, about a hundred yards up the slope, and he himself went round the corner of the wood, where he was just out of sight.

Presently, away inside the wood, they heard the tap-tapping of the beaters' sticks against the tree trunks. Both stood with their guns ready, craning their eyes up at the tree tops above which the pigeons would fly.

There was a sudden rush of wings, and a pigeon came right over Derry. He gave it both barrels, but never touched a feather.

Bang! Bang! came from the corner of the wood. He was just in time to see a bird double up in mid-air and fall with a resounding thump. It was Mr. Murston's first shot.

Then he saw Ned grinning at him. Ned had seen his miss. He bit his lip, resolved to do better next time.

Two birds came right over Ned. He, too, was not quite quick enough, and they went away untouched.

"Mark over!" came a cry, and here was a wild duck coming out on Derry's left, high over the top of the trees.

Derry flung up his gun and blazed away. To his delight, the bird crumpled up, but the pace of its flight took it right over the oak palings, and Derry saw it shooting down into the bushes on Mr. Coyle's side.

Forgetting all about the necessity of remaining at his post, Derry rushed after it.

Down came the bird, crash into the bushes, with the force of a projectile, and with the crash came a shriek, while two arms were thrown up, and then he heard the sound of a heavy fall.

Derry stopped, aghast! The dead bird had fallen on somebody's head—possibly on that of Mr. Coyle himself.

CHAPTER XII. — THE SECRET ROOM

DERRY paused a moment, but only for a moment. It was his fault that the man was hurt; it was up to him to go and find out the extent of the damage.

He glanced round, but Ned was a long way off, and in the act of blazing away at several pigeons which were coming over, one after another. He hesitated no longer, but laying his gun down, climbed the fence and ran towards the spot from which the cry had come.

The bushes were thick, and he had to force his way through them. He could not be quite certain of the spot and he stopped and called:

He began groping about again, and all of a sudden found himself standing on the edge of a small hollow. It was only about ten feet across, but quite five deep. And there, flat on his face, lay a man. He was in rough clothes and looked like a labourer, but he lay most uncomfortably still.

"Knocked him out. That's one sure thing," said Derry, as he jumped down into the hollow. "Are you hurt?" he asked anxiously, stooping over the man.

Next instant, something thick and heavy fell over him from above. Two powerful arms gripped him around the body. He found himself wrapped in the folds of a huge horse-blanket and flung to the ground.

For an instant he was so amazed that he lay still, but the next he was fighting like a tiger cat. That is to say, he was kicking for all he was worth. As for his arms, they were so pinned to his sides that he could not use them.

"Quick! We don't want them chaps t'other side o' the fence to hear what's a-going on."

To Derry it seemed that the pair of them both fell on him at once. He was crushed by such a weight that he could not breathe. The blanket cut off the air, he gasped for breath, and collapsed.

They were tied. By this time Derry was very nearly insensible, and quite unable to resist. The pressure slackened a little, then he was vaguely conscious of being picked up neck and crop, and carried away at a jog trot.

The blanket was still over his head, though now loose enough to give him a chance to breathe, but it was held around him so that he could not see or help himself in any way.

How far he was carried he could not tell, but presently he was slung bodily on to some sort of vehicle, a hand-barrow or small truck, and rattled away at a sharp pace. Then he was lifted again, and by the warmth of the air realised that he was being carried into a building of some sort.

A minute or so later he was dumped down on a floor, and the rug was jerked off him.

Two hard-faced men stood over him, and one he recognised at once as the fellow who had been lying on the ground in the pit.

"Got you, my young cock-sparrow," he said, and laughed as if he thought it an excellent joke.

"'Aughty?" sneered the man, but the other was rubbing the shin which Derry had kicked.

"Maybe you would, but you won't get it," retorted number one. "Leave 'im alone, and come on out. The boss'll attend to him all right."

They went, leaving Derry wondering who "the boss" was, and what on earth he wanted with him. The whole business had evidently been carefully planned, but what its object was he could not at present divine.

He managed to sit up and began to untie the cord securing his legs. Meantime he glanced around the room. It was a queer sort of place, being quite small though rather high in the roof, and entirely without windows. It was well ventilated, however, and lit by electric lamps. The only sound he could hear was a faint hum of machinery. It might have been a lathe or a dynamo, he could not tell which.

He got the cord loose, rose to his feet, and, of course, made for the door; equally of course he found it locked. He went back and began walking around the walls to see if there were any other means of exit.

Before he had got halfway round a key clicked in the lock, the door opened, and there entered as extraordinary a figure as Derry had ever set eyes upon.

He was a man of about fifty, tall, gaunt, a little stooped and dressed from head to foot in rusty black. He had a great domed skull, quite bald and shiny at the top, but with a thick fringe of hair all round.

His nose was huge and hooked, and on the bridge of it hung a pair of enormous horn-rimmed spectacles which magnified his curious grey-blue eyes. His chin jutted like the toe of a boot, and the skin of his face was the colour of old ivory.

Derry, looking at him, thought at first glance that his expression was rather benevolent, but the eyes made him doubtful. They were as cold and expressionless as those of a codfish. He, too, stared at Derry.

"Pleased to make your acquaintance, Mr. Holt," he said in a curiously soft, purring voice.

"You've chosen a queer way of doing it," replied Derry pretty curtly. "Are you Mr. Coyle?"

"That is my name, Cyprian Coyle," purred the other. "Yes, a curious way, I will admit, Mr. Holt. But necessary, unfortunately, necessary."

"Yes, necessary," went on Coyle. "And now that you are here I have a little proposition to put before you, Mr. Holt. I am at present engaged upon the construction of a new dirigible. I require your assistance. Your father, I know, was a distinguished engineer. I understand that you inherit his capacity. I am going to propose a partnership."

"I'm afraid that is impossible," he answered coldly. "I am already engaged by Mr. Murston."

"That, of course, I know," said Coyle amiably. "And that is why I took the precaution of bringing you here in the secret manner in which I did. But these little arrangements can always be broken, and I am prepared to offer you terms such as you will never obtain from Mr. Murston. Briefly, I offer you five thousand pounds a year for your services and the knowledge you will be able to place at my disposal."

"You have a quaint idea of business, Mr. Coyle. I have not the least intention of breaking my agreement with Mr. Murston."

"Think!" said Coyle, and there was a sudden menacing gleam in those queer eyes of his. "At present I am treating you generously. But if you refuse my terms you will find yourself in a very different position. You will remember that you are completely in my power."

"Oh, what's the use of talking nonsense like that?" retorted Derry impatiently. "This is the twentieth century, and we are only forty miles from London. You can't do the robber baron act."

"You are young, my friend," answered Coyle, with ominous quietness. "There are many things which you do not yet understand. I repeat, you are absolutely in my power."

"And what do you think that my friends will be doing when they miss me?" returned Derry sharply.

"They will very probably send here to inquire after you. I shall tell them we have not seen you. My people will bear me out. If they still doubt, I shall ask them to search the house. But they will not find you."

Coyle's voice gave Derry cold chills. He spoke with an air of such absolute certainty that Derry felt that he must be right.

"For good, or for bad. It depends upon yourself," he purred. "But not here, my young friend—not here."

CHAPTER XIII. — A BLIND ALLEY

AGAIN Derry felt a cold shiver down his spine. This man meant what he said. That was beyond any doubt whatever. He, Derry, was to be kept prisoner until he agreed to Coyle's suggestion. He was to give up the secrets of the new dirigible, or, if not, be carried away to some remote spot and buried alive perhaps for years. It was a cheerful prospect, and Derry felt that he could have kicked himself for tumbling into such a trap.

Those cold, blue eyes were bent upon him. It seemed that Coyle could actually read his thoughts.

"No, there is not any chance for you, Mr. Holt," he said softly. "None whatever. If you decide at once to enter into partnership with me, you will get well paid and well treated. If not, the offer of pay and partnership lapses, and you will be kept a close prisoner until you divulge the secrets which I am determined to possess. You will then get nothing but your liberty in exchange for these secrets."

"You may keep me for ever," he said, "but neither you nor James Spain will ever get a word out of me."

"You are young," Coyle continued calmly, "young and foolish. But time will cure that. I can afford to wait, but—"

A sharp tap at the door interrupted him, and he went quickly towards it and opened it.

"Whittaker wishes to see you, sir," began a voice outside. "It's someone from Cloam, sir."

"I will leave you to think it over," he said in that queer, thick voice of his. "I am now about to get rid of your inquiring friends. But I shall be back shortly—quite shortly."

The door closed, the key turned in the lock, and Derry was left alone. For the moment he felt desperate. His knowledge that Mr. Murston and probably Ned were within a few yards and yet that it was impossible for him to let them know drove him nearly crazy. He felt like shrieking at the top of his voice.

But Derry had plenty of self-control, and instead of shouting stood perfectly still, took a long, deep breath, and got a good hold on himself.

Meantime, his brain was working sixteen to the dozen; and he was struggling to think of some way out of this awful mess. Coyle had said that he could not be kept here. This meant, no doubt, that he would be carried away to some secret retreat—very likely the one that Spain used—and hidden there beyond all reach of help.

Desperate cases call for desperate measures, and a plan flashed like lightning into Derry's mind. A mad plan, but it seemed at the moment the only possible one.

Coyle was coming back. He would be alone. If he, Derry, could only succeed in knocking the scoundrel out, he might take his key from him, and so escape from the locked room. Whether he could get out of the house was another question, but it would be a chance at any rate.

His eyes roved around the room in search of a weapon of some kind. A poker was the first thing that occurred to him, but there was no fireplace. The room was heated by pipes. There were chairs, but they were too big and heavy, and too solid to break up.

Then suddenly he spotted an electric lamp standing on the writing table. It was one of those movable arrangements with a wandering wire lead. He sprang across and grasped it. It was about eighteen inches long, made of brass, with a heavy butt or pedestal.

"The very thing!" he murmured, and, whipping out his knife, sawed through the wire. He threw the shade aside, removed the bulb, and swung the thing in his right hand.

The waiting was fearfully trying, and Derry's thoughts were not pleasant. Mind you, it is one thing to hit a man in a fight, quite another to lie in wait for him. This was not the sort of business that Derry liked at all, yet it seemed the only thing to be done.

Minutes passed. They seemed like hours. At last a scratching sound came to his ears. The key was being pressed into the lock.

The door opened, and in came—not Coyle at all—but a man whom Derry had never seen before, a short, thick-set fellow in a blue serge suit.

He was quick, too. But down came Derry's weapon with a thud on his head, and he fell with a crash on the floor. Derry made certain that the noise must have been heard all over the house.

He paused an instant, listening hard, but there was no other sound. Outside the door was a long passage leading to a flight of steps. The passage had no windows, and was lit by an electric lamp.

Derry's first impulse was to bolt, but he suppressed it. Quick as a flash he took the key from the lock, closed the door, then with feverish speed pulled off his victim's clothes.

The man was only stunned. He might come round at any moment, and the speed at which Derry got out of his own clothes and into the blue serge was a record.

At the top of the flight of steps was another door. This, too, was locked, but he found a key to fit it in the trouser pocket of the serge suit.

He opened it very cautiously and peered out. He was in another passage, one floored with wood and covered with linoleum. To his left, at the left-hand end of the passage, was a swing door; to the right were two other doors, and then at the right-hand end of the passage a third. The passage was dimly lit by a small window close to the roof.

Again he paused, but still there was no sound. He had not, of course, the faintest idea where he was, but he decided that the swing door probably led into the front of the house, while that at the other end was either a back door or perhaps that of the kitchen.

If he went the front way, the chances were that he would run into Coyle, and the idea filled him with such horror that—unwisely, as it afterwards proved—he decided to try the back.

He went down the passage on tip-toe, and put his ear against the door so as to make out if anyone were on the other side. At this moment he heard hasty steps approaching the swing door, and like a flash flung open the door in front and slipped through.

It was Coyle's voice, and Derry knew he must have seen the opposite door close. He stood an instant, breathless, looking all round. He was not outside, but in a kitchen. For the moment there was no one in the room, but pots were boiling on a bright fire, and a pastry board, rolling-pin, and other utensils ready on the table. The cook was evidently away for only a minute.

Derry hesitated no longer. There were two doors, one opposite. He chose the latter and darted through it, only to find himself in a scullery, with no way out. No way, that is, except a window with iron bars across it.

Derry was at his wit's end. He had to hide somewhere. The question was, where? He saw a cupboard, and opening the door managed to squeeze himself into the bottom of it among a lot of pots and pans, potatoes, and onions.

Coyle's step was plainly audible as he strode quickly through the kitchen. Derry's heart was in his mouth, but Coyle did not enter the scullery. He opened the other door.

"Strange!" Derry heard him mutter in that queer, purring voice. "I would have vowed it was Dalkin, though what the fool was doing here I can't imagine. Mrs. Burns!" he called.

"You are blind and deaf," snapped Coyle, who was clearly in a very bad temper. "Dalton or someone came through the kitchen a moment ago. He must have gone out into the yard."

"He didn't come out in the yard, sir. I'd have been certain to see him," replied the woman.

"He might have gone into the scullery, sir, to wash his hands," suggested Mrs. Burns.

Derry's heart fell like mercury in an ice bath. His last hope of concealment was gone. He grasped his lamp standard firmly. Whatever happened, he would not be caught a second time without putting up a fight for it.

CHAPTER XIV. — THE SECOND YARD

PURPOSELY Derry had left the scullery door ajar as he had found it. From his uncomfortable refuge in the cupboard he could not see the door, but he heard it pushed sharply open.

He could almost feel Coyle's eyes upon the cupboard, and in that moment he gathered himself to leap out and tackle the fellow.

"Doesn't seem to be," growled Coyle. Then suddenly he burst out savagely: "What does this mean? What trick are you playing on me, woman? I don't see ghosts, and I can swear that someone came through the door into the kitchen. I believe you are hiding someone here."

"Me hiding someone!" retorted Mrs. Burns, in a tone that was every bit as angry as Coyle's. "Me hiding someone! That's a nice thing to say to a respectable woman that never even took a basin of dripping out of your kitchen. I won't stand it. I won't put up with it. I'll go this very day as ever is."

Men he could tackle, but he was afraid of an angry woman. Besides, he evidently did not want to lose his cook. Tight as Derry's fix was, he almost laughed as he heard Coyle actually apologising.

Then, to his intense relief, Coyle left the kitchen and went back into the passage.

But his feeling of relief did not last long. Next thing that would happen, Coyle would go down to the underground room, find his man on the floor, and then the fat would be in the fire with a vengeance. He himself had to get out—and quickly, too, for once Coyle found he was gone he would go through the house with a fine tooth-comb.

The question was how to get out. Mrs. Burns was still in the kitchen and likely to stay there. She was in a temper, too. He could hear her rattling her dishes angrily.

It seemed to Derry there were only two things he could do. One was to make a bolt for it, the other to march out into the kitchen and throw himself on the mercy of the cook.

He never wasted time in making up his mind, and at once he decided on the latter course. It was quite clear that Mrs. Burns didn't like Coyle, so she might be willing to assist Derry.

With some difficulty he crept out of his cupboard and went to the door of the back kitchen. The cook was standing at the range, with her back to him.

Mrs. Burns started violently, dropping a ladle with a clatter. She spun round and Derry saw that she was a big, square-built woman with great bare arms, and looking as strong as most men.

"It's all right, Mrs. Burns," said Derry. "I'm not Dalkin, although I've got his clothes on, but I'm not a burglar."

"My name is Holt, and I've been decoyed in here by a trick," explained Derry rapidly. "Mr. Coyle locked me up down below, but I got out. Now I want to get clear away altogether. Won't you help me?"

Mrs. Burns stared at him doubtfully. For some seconds Derry had no notion whether she meant to shout for help or not. But he stood quite still, and looked at her, and even managed to smile.

"There's funny things goes on in this house," she said. "And what did he want off a boy like you?"

"Something as you invented yourself? Well, you must be a clever one, I'm sure. Yes, and you've got a clever face, too. Well, I never! Think of him a-shutting you up like that!"

Derry was aching with impatience, but did not dare to show it. Everything depended upon this woman.

"He'll catch me again, if I don't hurry off at once," he ventured. "And I shan't get a second chance. I'm sure of that."

"Yes, but that's no use to you," said Mrs. Burns. "The gate is locked, and there isn't no way out of it. You ought to go out by the front."

"He's found that the door is locked," whispered Derry. "I must be off. I'll chance the yard. Perhaps I can climb over the wall."

But Derry had already bolted through the door, and closed it behind him. The first thing he realised was that the weather had changed. It was raining a thick drizzle. The dusk of the winter afternoon was beginning to close in.

He glanced round. The yard was a good size, and flagged. The house bounded one side of it, outbuildings two others, while the fourth was guarded by a high wall in which were a pair of heavy, solid, wooden doors.

It did not need a second glance to show him that these were padlocked, and that the wall itself was far too high to climb. At first sight it did not seem that he was any better off than he had been in the house.

But he could not stay where he was. He heard Coyle's voice again in the distance, and made one wild bolt across the yard.

A door stood open, and scuttling in, he found himself in a disused stable. There were two loose boxes, but no way out. He paused, uncertain what to do next, when suddenly he heard the kitchen door flung open with a crash.

Looking round in sheer desperation, he noticed a square hole in the ceiling. It was the place through which the hay was dropped into the manger below.

There were footsteps on the flags outside. Quick as thought, Derry made a spring on to the manger, reached up, and was just able to catch hold of the edge of the flooring above. For a youngster as active as himself that was enough, and in a twinkling he had swung himself up and was standing panting in a long, low-roofed loft. A few bundles of mouldy hay lay stacked against the far wall, and Derry thought that at a pinch he might hide among them.

He stood and listened, and heard two people come running across the yard, and plunge through a door somewhere below. The one thing he was grateful for was that it was not his stable they had entered.

"You don't know as he's come across here, sir," answered another voice. "How do you know he didn't go back into the house?"

"Because I should have seen him. He's come out this way. Open those cupboards, look in among those bags. He's here somewhere."

Then came a bumping, clattering noise, as if a lot of packing- cases were being shifted.

Derry was again at his wits' end. He had half a mind to drop, bolt back, and chance getting through the house before they could catch him.

He had almost resolved to try this when he noticed a sort of dormer window in the sloping roof of the loft. It faced out the other way from the yard, but was so covered with dirt and cobwebs that no light came through it.

Still, it was a window, and would probably open. If he could once climb out on the roof surely he would find a chance to get away.

To his joy the window opened fairly easily, and Derry did not waste any time in worming his way through.

He was now looking down into a second yard with buildings all around it. Some were quite new, and appeared to be workshops. But these he hardly glanced at. All his attention was concentrated on an object in the centre of the yard. It was a balloon—a small balloon ready filled with gas and swaying slightly in the light breeze. The rain dripped from the yellow fabric of its gas- bag.

CHAPTER XV. — THE LONELY DOWN

TO Derry, accustomed to aircraft almost since he could walk, the sight of the balloon was like that of a lifebuoy to a drowning sailor. If he could only reach it, he felt perfectly certain that he could escape.

The roof was slated, and being wet was very slippery. But it was not very steep, and from its edge it was not more than ten feet to the ground.

He flattened himself out on the wet slates and managed to reach the gutter in safety.

Here he paused and listened. From the noise inside the building, Coyle and his man seemed to be still turning things upside down, and in spite of everything Derry smiled as he thought how little they suspected where he really was.

Then he took good hold of the gutter with both hands and let himself down until he was dangling at arms' length. It was a biggish drop, but he had to take his chance, so let go. He alighted with knees well bent and luckily took no harm; bending almost double, he bolted across to the balloon, and jumped into the basket.

It was moored to sandbags, but Derry did not wait to loosen the knots. He still had his knife, and with it made short work of the ropes.

So long as he was on the far side of the balloon he was all right, for the sides of the basket hid him, but when he had to come round the nearer side he felt horribly nervous. There were windows all along the row of outbuildings, and, although the light was failing, Coyle could hardly help seeing him.

"In—in the balloon, sir." The man was actually stuttering with excitement. "And—and he's c-cutting the ropes."

Derry sawed furiously at the ropes. Only two were left, but his knife was blunting. The window was halfway up There it stuck.

"Out of the way!" howled Coyle, and, pushing his man aside, seized the sash. Still it stuck.

There was a pause of perhaps five seconds. Derry sawed with all his might, but all the edge was gone from his blade, and he was only halfway through when there came a terrific crash, followed by a splintering clatter of broken glass.

Out of the tail of his eye he saw Coyle hurl himself through the broken window and come rushing across the yard.

Raising the knife, he made a last frantic slash. The blade went through, but the balloon did not lift. For the moment Derry had forgotten the heavy ballast in the basket.

Coyle, in a furious rage, was on him, when, quick as thought, Derry stooped, and, lifting one of the small but heavy bags of sand in both hands, hurled it at his enemy.

The bag caught Coyle full in the chest and fairly swept him off his feet. He lay like a log.

His man was close behind, a thick-set, hard-faced fellow, but Derry had no fear of him. He was tingling with excitement. Seizing a second bag, he swung it as if it had been a feather and flung it at the man. Though it failed to reach its target, its weight made all the difference. As it left Derry's hands the balloon jerked upwards, rising with such speed that Derry was flung down into the bottom of the basket.

Scrambling breathlessly up, he looked over. Coyle's house lay like a toy beneath him, while Cloam, looking equally tiny, was about two miles away. The balloon was still going skywards, and a sou'-westerly breeze was carrying her right away from both houses.

He seized the valve cord and pulled it. But before enough gas could escape to bring the balloon down he was in a cloud—in a fog too thick to see fifty yards.

It was an ugly situation to be in, for night was coming on, and, of course, he could not tell where he was going. And landing a balloon is not an easy job, even in broad daylight. In the night it is a most perilous business. You may get into trees, houses, or telegraph wires, or you may drop slap into a river or lake.

There was a barograph in the balloon. Glancing at it, Derry saw the needle moving slowly upwards; he gave a sigh of relief. At any rate, she was coming down. But, of course, there was much more wind up here than on ground level, and he knew that he must be travelling pretty fast.

It was a good ten minutes before she dropped clear of the cloud again, and now it was really twilight, with the rain thicker than before. Derry looked round, but could no longer see Cloam or tell where he was.

Beneath was a big, bare down. He took his chances and pulled the ripping cord. That settled it, and down she dropped, very fast at first, but presently she parachuted and fell more slowly.

Luckily there was hardly any wind at ground level, and Derry made a good landing. He did not worry about the balloon; leaving her where she was, he made off in the direction of a road which he had spotted as he came down. He felt sure he would soon meet someone who would put him on the right track for Cloam.

But this was evidently a lonely part of the country, or else the rain had kept everyone at home. The wet, brown road was empty, and Derry had not the faintest notion in which direction to go. During his plunge into the mist he had lost his bearings completely.

It was rapidly getting dark, Derry was wet to the skin, he was very hungry and very weary.

Since it was no use standing still in the rain, he took the way which led downhill and started off. If there were no wayfarers, surely, he thought, he must find a house.

But after walking half a mile he could still see no lighted window, and the country seemed in the dim light to be becoming more and more empty and dreary. Also the rain was now a steady downpour, and it was horribly cold.

On again, and still no sign of life. It had begun to look like a night in the open, which was anything but a cheering prospect, when suddenly Derry heard a sound in the distance.

He stopped and listened eagerly. Undoubtedly the sound was approaching. Presently the darkness was illuminated by two shafts of white radiance, and he was able to see the car roaring up the slope towards him.

His spirits rose with a bound, and he stood stock still in the middle of the road, ready to stop it. There was the chance that it might be a car from Cloam. Whoever it was, they would surely give him a lift back to civilisation.

The slope was steep. The car dropped to second speed, and came on at no more than twelve or fifteen miles an hour. Presently the glare of her big electric head-lights fell full on Derry's wet and lonely figure. He waved his arms.

The car was an open one with a touring body. There were only two people in it, one driving, the other beside him.

The driver saw Derry. Derry saw him turn quickly to his companion, and at once the car slackened speed. Derry ran up to it with joy.

"I'm so sorry to have to stop you," he said, "but I'm lost. Can you tell me the way to Cloam?" The passenger turned his head towards Derry. It was Coyle.

CHAPTER XVI. — HIDE AND SEEK

THE shock was so great that for a moment Derry stood staring like a bird fascinated by a snake. Coyle caught him by the lapel of his coat.

The motion broke the spell which had held Derry, and, hardly knowing what he did, he struck at Coyle with all his force.

Coyle jerked back to escape the blow, and as he did so loosened his hold on Derry's coat. Instantly the boy spun round and bolted.

"Stop him!" roared Coyle, springing up and seizing the handle of the door to open it.

The delay, brief as it was, gave Derry his chance. Clearing the low hedge at a bound, he raced away across the open down.

At first he paid no attention to where he was going. His only idea was to put as much space as possible between himself and Coyle. But before he had run far he began to realise that the space was lessening rather than increasing.

Coyle's legs were long, and his tumble by the balloon did not seem to have done him much harm, while his man could run faster than he. What was more, both of them were in deadly earnest. It was not only that Coyle wanted Derry's secret, but that now Derry knew too much of Coyle's secrets, which the latter could not afford to give away.

Glancing back over his shoulder, Derry saw quite plainly that his pursuers were gaining, and realised that, if he had to keep to the open, he was bound to be run down sooner or later.

Looking despairingly around, he saw, a good way ahead, what looked like a wood, though the light was too bad and the rain too thick to be sure of anything beyond about a hundred yards. He headed for it, straining every nerve to reach it before his pursuers.

As he got nearer, he saw that the "wood" was a stretch of bracken-covered ground with small thickets of thorn and pollard oak—a big rabbit warren, in fact.

Putting on a terrific spurt, Derry got into it some fifty yards in advance of the chauffeur who, in his turn, was a good bit ahead of Coyle, and made for the thickest of the cover.

Next moment Derry was in the midst of a tangled mass of thorns and brambles. It was too thick to run through, so, flinging himself down, he started to crawl through it. He did not go straight ahead, but turned uphill. He felt almost certain that the chauffeur and Coyle would think he had gone straight.

Breathless and almost exhausted, Derry crept into a patch of dead tall bracken, and lay still. His heart was thumping so that he almost feared that the chauffeur would hear it, and in spite of the cold, perspiration was pouring down his face.

The chauffeur crashed through the thicket like a mad bull, but, just as Derry had expected, kept straight ahead.

"Are you sure he's gone ahead? He's as cunning as a fox. He may have dodged. Stop plunging like that," he added fiercely. "Keep still a moment. Listen!"

Silence fell, silence broken only by the raindrops dripping from the bare branches of the stunted trees.

"He can't be far away," returned Gresson sulkily. "He wasn't no distance in front o' me when we came to this here wood."

"No, he can't be far, but it's a filthy place to hunt through, and it's getting darker every minute. Start and beat up and down, Gresson."

Derry's heart turned to lead. He did not see how he could possibly escape if they set to searching systematically.

Derry heard the man's heavy step crashing through the fern, and apparently coming straight towards him.

He was strongly minded to spring to his feet again and bolt. But if so, he would have to run uphill, and he knew very well that he would not stand a dog's chance. What he did do was to start creeping again, trusting that Gresson's heavy boots would drown the sound of his movements.

As Gresson came straight towards him, Derry dropped flat, and lay absolutely quiet, hardly daring to breathe. Next moment Gresson almost stepped upon him, yet in the darkness never saw him, and trampled past.

The escape was so narrow that for the minute it left Derry quite limp. But he pulled himself together, and, as soon as Gresson was a little way off, started crawling again.

Gresson turned, and once more came straight at him. Derry had given himself up for lost when he heard Coyle's voice from some distance away:

Round went Gresson like a top, and by the time that Derry had got his breath again was nearly fifty yards down the hillside.

"In here!" he heard Coyle shout. "That's where I heard him. Whatever you do, don't let him slip past."

"What luck!" said Derry fervently, and inwardly he breathed a blessing on the rabbit which had lured his enemies off the track.

He did not waste time in watching them, but began to crawl away as fast as ever he could go, keeping uphill. There was not so much cover up here, but, luckily for him, it was so nearly dark that this did not matter greatly. In the distance he could hear Coyle exhorting Gresson to rout the young vermin out.

Suddenly Derry found himself on the edge of a deep hollow. It was one of those long troughs which you so often find running across the side of a chalk down. So far as he could see in the thick dusk it seemed to lead right back in the direction of the road.

Like a flash, it came to him that this was his chance. His pursuers would hardly dream of his doubling back on his tracks. Besides, he would be able to stand upright and run along this hollow without any risk of their seeing him.

But luck was still against him. In the gloom he ran right into a flock of sheep, sheltering from the cold rain in this fold of the hills, and the silly creatures stampeded, careering wildly in every direction.

Sure enough, it had. At once there was a shout from somewhere down the hillside.

"He isn't here at all, sir. That's him away up the hill there. See them sheep a-running?"

With a sinking heart, Derry realised that it was all to do again, and that he was less fit than ever for a long run. If he could not find some hiding-place, or some way of dodging his pursuers, he was bound to be caught.

He had gone only what seemed a very little way before he heard Gresson's feet thudding on the short turf, and getting closer every moment.

He spurted once more, but there was no cover of any sort, and he knew he could not go much farther. Just as he was on the point of despair, a new sound came to his ears. It was the steady throb of a motor-car engine. Suddenly he realised that he was right back on the road, and that he had reached it at the very same point at which he had left it.

And there, not fifty yards away, was Coyle's own car, with the engine still running.

The knowledge put new life into Derry; he redoubled his pace, and made straight for the car.

As he came up out of the dip Gresson saw him, and the yell he let out echoed across the dark, wet hillside. But Derry only ran the faster, and with a final burst reached the car, into which he fairly hurled himself.

Gresson was less than fifty yards away. Derry could hear the man's panting breath as, with trembling fingers, he took hold of the hand brake and flung it out of gear. The gas control was unfamiliar, and at first he cut it off. The engine ceased, and he gave himself up for lost.

But the car was standing on a good slope. The moment the brake was off she started. Derry had sufficient presence of mind to let her run a few yards before giving her gas. To his intense relief the engine responded instantly. She jerked forward sharply.

But the danger was not over. As she started Gresson came charging at the low hedge on Derry's left. He jumped it clean, but came down badly, and staggered and fell. Those two or three seconds made all the difference, giving Derry time to fling the change gear lever into top.

Gresson rushed sideways at the moving car, and actually managed to catch hold of the back of the tonneau.

Derry did not look round. Instead, he gave the car full gas, and in an instant she was leaping down the slope at a most perilous speed.

There came a yell of terror; Derry was conscious that Gresson had been forced to let go. At last he had succeeded in shaking off his pursuers. He cut off gas, but did not brake, and shot onwards down the long slope.

Luckily for him, the road was straight and open. As it was, he was going a good fifty when he reached the bottom of the hill, and the impetus of his rush carried him halfway up the opposite slope. Now he began to drive more quietly, and ventured to look back. There was no one in sight, nor could he hear any sound.

He reached the top of the next hill, where, to his left, he saw the lights of Cloam among the trees.

CHAPTER XVII. — THE MESSAGE

IT was Colvin, Mr. Murston's own man, who met Derry at the door. He stared for a moment in blank surprise at the wet, muddy object in the ill-fitting blue serge suit, then suddenly turned round, rushed to the door of the study, and pulled it open.

As he spoke he seized Derry by both hands and drew him to the fire. Then he turned to Colvin.

"Get a hot bath for Mr. Holt, and a change. My poor boy, what have they been doing to you?"

"Coyle kidnapped me, sir," replied Derry. "He's in with James Spain. Mr. Murston, we must not lose a minute.. We must arrest him at once."

"Coyle!" repeated Mr. Murston in a tone of utter amazement. "You don't mean that?"

At that moment some hot tea was brought in, and in a few rapid sentences Derry told Mr. Murston what had happened.

"Of all the impudence!" he exclaimed. "Spain's backer living next door to me, and I never suspecting it for a second! But you are right, Derry. We must be after him at once. Ned is not in yet. He went to Fansham in one of the cars to inform the police of your disappearance. But I have three good men on the place. I'll go at once."

"We shall want more than three, sir," declared Derry. "Coyle has a lot of men there. And, remember, he is desperate."

"I'm not afraid of him. All I am afraid of is that he may have cleared out before we can get there. But I'll telephone the police."

"You! You'll go straight to bed, my lad," retorted Mr. Murston. And beg as he might, Derry found the millionaire absolutely inflexible.

Derry was disgusted, and, though he did not show it, badly upset. He was anxious, above all things to give a hand in bringing this fellow Coyle and all his crew to book. And he had good reason to think that his own knowledge of Coyle's house would prove useful.

But Mr. Murston's word, when he once made up his mind, was law, and Derry knew him too well to go on arguing. He went to his room, as ordered, but instead of going to bed changed his wet things for dry ones, and waited by the window to see Mr. Murston start.

He had not long to wait. The millionaire's household was singularly efficient, and in five minutes a big touring car came round. It was driven by Bayliss, Mr. Murston's chauffeur, and beside him was Noakes, the keeper. Mr. Murston came out, accompanied by the butler, Colvin, and Derry noticed with satisfaction that all had heavy sticks. He thought, too, that he saw a gun beside Noakes.

The car drove quickly away, and Derry bit his lip as he saw the glow of the big head-lights disappear around the sweep of the drive.

As he turned back to the fire, there was a tap at the door, and Mrs. Ames, the housekeeper, came in with a tray.

"You must be starved, sir," she said. "I've brought you some supper. You must eat it at once, and then get to bed."

"Gracious, Mrs. Ames, here are provisions for a week. All the same, I am pretty hungry, and I dare say I shall make a good hole in them."

It was a regular feast the good woman had brought up. There was a cup of hot soup, a plate of cold turkey and tongue, a dish of trifle with whipped cream, and a couple of great hot-house peaches by way of dessert.

Derry had just finished his supper when he heard quick steps on the porch. His bedroom window happened to be almost over it. Next minute Mrs. Ames came up again. She was in a great hurry, and Derry could see by her face that she was very much upset.

"There's a man below asking for you, sir. He comes from the master. I'm afraid there's something wrong."

"Don't say that scoundrel Coyle has got hold of him! I begged him to wait for the police, or to let me go with him."

As Derry spoke he kicked off his slippers and thrust his feet into a pair of boots.

A man was standing just inside the hall, a youngish man and not bad looking. He had the appearance of a gamekeeper, but Derry was sure he had not seen him before.

"My name is Kane, sir. I am keeper to Mr. Humphreys over at Keir. I've been out late, watching for some poaching chaps, and was coming home past the gate of Mr. Coyle's place, when I heard a crash and cries for help. The noise came from the drive, sir, and I ran up and found a car upset. It was Mr. Murston's car."

"Well, sir, seemed to me as there'd been some dirty work. The road was cut away like."

"I'm afraid he is, sir. There was three men with him and all is damaged except one. Mr. Murston was a-calling for you, sir, so I thought I'd best come along at once."

"Yes, of course, you were quite right. I must telephone for a doctor. Then I'll be with you."

It took Derry just about two minutes to call up the doctor from Fansham. Then snatching up a heavy stick from a rack in the hall, he joined Kane.

Derry was desperately anxious. If Mr. Murston were badly hurt, this was the end of everything so far as building the new airship went. But there was much more than that. During the few weeks since he had first met the millionaire, Derry had grown very deeply attached to him. To lose him would leave a blank which nothing could fill.

Kane walked at a great pace; but, tired as he was, Derry kept well up. The drive up to Cloam was edged with big beech trees, and though they were now leafless it was very dark underneath. The night had closed in as black and gloomy as the afternoon. Though the rain had stopped, a heavy mist clung to the wet ground.

They reached the drive gate and came out on the road. Kane crossed to a gate opposite.

He found himself in an open field. It was a little clearer here, and through the gloom Derry fancied he saw something like a large haystack a little distance ahead.

Instead of answering, Kane sprang upon him suddenly, and taking him completely by surprise bore him to the ground.

CHAPTER XVIII. — A DRAWN GAME

BEFORE Derry knew what was happening, he was on his back on the sopping grass, with the man Kane kneeling on his chest. He was trapped for a second time that day, and the knowledge drove him perfectly frantic.

But Kane had twice his strength, and, holding him down with one hand, put two fingers of the other in his mouth, and gave a piercing whistle.

It was instantly answered from the middle of the field, and it flashed upon Derry that the object he had seen, and which he had at first taken for a haystack, was really an airship. For all he knew, it might be Spain's own craft.

Once they got him aboard her, all hope was lost, and in desperation he shouted at the top of his voice.

That was all he got out. With a threat, Kane caught him by the throat, choking him so that he could not breathe.

He was doing it. For a moment or two Derry struggled vainly, then stars began to dance before his eyes, his chest felt crushed, and he collapsed and lay still, almost unconscious.

Kane slackened his grip a little, and the air began to whistle back into Derry's empty lungs, but Kane still kept hold of his throat, ready to cut off any attempt at a shout.

Derry heard quick steps thudding across the wet turf. Men were coming from the airship. For the first time that day a dull cloud of despair fell over him, and he felt that he could no longer resist or do anything to help himself.

"What luck!" answered another voice. It was not Coyle's, but that of one of his men. "This is as good as fifty quid in our pockets. The boss'll be tickled to death."

The two men reached the spot together, and one, pulling out an electric torch, switched it on, while the other took a coil of thin rope from his pocket.

"We'll tie him up this time, and make sure of him," he remarked. "It don't do to take no chances. The chap's as slippery as an eel."

"Right you are," said Kane, with a coarse chuckle. "Give us the cord. I'll make a job of it. I'm not going to lose that fifty—not if I knows it."

The moment he removed his weight from Derry, the latter made a last struggle to get up.

"You would, would you?" snarled Kane, knocking him down again. "Here, hold him, you chaps," he went on angrily.

Both the others grabbed Derry, and pressed him back against the soaking ground. He could feel the ice cold water wetting him to the skin.

"Turn him over," ordered Kane. "I'll tie his hands behind him. Be sharp, now. We'll have the boss after us in about two shakes."

Derry was turned roughly over on his face, and Kane, seizing his wrists, forced them together behind his back. Dazed with the blow, Derry was beyond struggling, but his feelings were too bitter for words.

He felt the cord being twisted roughly round his wrists. The next thing he knew was a thud, and Kane dropped like a sack right across him.

Was it Ned's voice, or was he dreaming? Derry hardly knew. Using his last ounce of strength, he wriggled out from under Kane's insensible body, and staggered to his feet.

A second man lay close beside Kane. It was the one who had held the torch. A few yards away Ned Barlow and the third man were locked in one another's arms, stamping up and down, battling furiously. Neither said a word, but Derry could hear the sound of their hissing breath. He could hear something else, too, and that was a rapid patter of feet coming from the direction of the airship.

It was no time for hesitation. Though his head was spinning so that he could hardly stand he staggered across towards the two struggling men, and getting behind Ned's opponent, caught him by the collar and kicked his legs from under him.

Down he came, Ned on top of him. All Ned's eleven stone struck the fellow full in the stomach, knocking every ounce of breath out of him, and the man lay gasping like a fish out of water.

"Come on," gasped Derry hoarsely. "There are more coming. Give me an arm, and make for the stile."

In an instant Ned's strong arm was round Derry, and the two were hurrying back the way they had come.

The other man must have stopped to examine the scene of the struggle, for the two reached the road without interference. There stood a car, head-lights blazing, engine still running. Ned picked Derry up bodily, hoisted him in, then sprang past him into the driving seat, and in a twinkling the car was speeding down the road.

"Lucky you came when you did, Ned," panted Derry. "They had me that time. No, don't go into Cloam. Drive to Coyle's place. Mr. Murston's there. If we can only get to him in time we may be able to stop the airship. It's Spain's, I believe."

"Coyle's in with Spain. It was Coyle's men who got hold of me this morning. Coyle was going to hang on to me until I told him about the new engine. I got away and back to Cloam. This was his second shot. Tell you all about it later. Our job now is to get hold of Mr. Murston and his men, and to try to bag the airship. If we don't, Coyle will get away altogether. He knows we're after him."

"I believe so. Yes, I can see the lights of the house. Wait, I'll get out and open the gate."

He got out stiffly. He was sore all over. At that moment the head-lights of another car glared out, coming down the drive.

"What—you!" he cried, and his deep voice boomed angrily. "I thought I ordered you to bed, Derry."

"I know you did, and I was going, when a message came that you were in trouble. It was a fake. They caught me again, and if Ned hadn't come up when he did they'd have had me. There's an airship in the field opposite Cloam gate. Spain's, I expect. We came for you to try to catch them."

Derry poured out his news all in a breath. Mr. Murston acted with his usual decision.

In less time than it takes to tell the big car was roaring down the road towards Cloam gate. The distance was only half-a- mile, and they covered it inside a minute.

The whole six filed out, and charged over the stile across the field. In his excitement Derry forgot his bruises, and ran with the best.

Ned, with his long legs and great running powers, gained on the rest, and led them all.

Derry heard an ominous and all too familiar sound, and dropped flat on his face The others all did the same. Only just in time! Next moment the night was split by a glare of flame, and the cracking explosion of a large bomb. A fountain of turf and mud rose geyser-like in the darkness, and fell thudding over acres of ground.

"I see they have," said Mr. Murston, as he stared skywards at the long, dim bulk of the airship. "They've got away, but that's about all they have done. They haven't got Derry or the new engine or anything else they were after, while we have Coyle's place, his laboratory, and all sorts of valuable materials. I think, on the whole, the luck is with us. Let us all go back to Cloam and to bed. To-morrow we'll talk of plans, and of how to defeat Coyle and Spain."

CHAPTER XIX. — THE TRIAL TRIP

ON a bright summer morning some four months after the events recorded in the last chapter Derry Holt sat in his office at Marchester.

It was a room very different from the queer little dog-hole in which we saw him on the night of the previous Christmas Eve. It was far larger, more airy. It was neatly, though not expensively furnished, and the desk at which Derry sat was a rolltop of polished oak, fitted with all modern conveniences.

The post had just come in, and Derry, quickly sorting the letters, came upon one addressed to "Derry Holt, Esq." in a big, strong handwriting which was pleasantly familiar. He cut the envelope open with a slim steel paper-knife, and unfolded a large square sheet of paper.

He had only just begun to read it, when the door burst open with a bang, and in rushed Ned Barlow. He looked bigger and fitter than ever, and in his hand he held a newspaper.

"Last night, at a few minutes past eleven o'clock, the Northern, Ltd., was stopped by a danger signal at a place called Hawes Bridge in Northumberland. The driver had hardly pulled up before two armed men sprang upon the footplate of the engine, and putting pistols to his head and that of his fireman forced them to uncouple the engine and draw off to a little distance.

"In the meantime, other men—six at least in number—entered a goods van in which was a large sum in gold consigned from the Bank of England to the Bank of Scotland. The bank official in charge, was ordered to give up his keys. Resisting this order, he was brutally shot down.

"The guards were held at pistol point, while others of the gang proceeded to burst open the safe containing the gold with nitro-glycerine or some similar explosive.

"The work was done with extraordinary deftness and speed, and inside twenty minutes from the time of the train being stopped, the bandits were away with a sum of gold said to exceed twenty thousand pounds.

"It was a dark, misty night, and the robbers were out of sight almost at once. The driver, as well as several of the passengers, are ready to swear that, shortly after the robbers left, they heard the sound of an airship's engines.

"Help was at hand within a comparatively short time, but though all the surrounding towns and villages were warned at once by telephone, no sign of the bandits has been seen up to the time of writing.

"Scotland Yard is definitely of the opinion that the outrage is the work of the notorious James Spain, the air-pirate who, some months ago, it will be remembered, held up the liner Leviathan, and, though chased by a seaplane, made good his escape."

"Of course, it's Spain! I thought it was about time for the beggar to start something. He's been lying low now ever since the Leviathan job."

"Of course, it's Spain," agreed Ned. "But, I say, Derry, this is the worst thing he's done yet. It isn't only the robbery. He's killed an official of the Bank of England. The country isn't going to stand that sort of thing. The Government's bound to move. Spain will find that he has stirred up a regular wasps' nest."

"They'll have to do something, certainly, but I don't suppose it will be much use. There was the mischief to pay after the Leviathan business. They had 'planes and things out all over the show, yet they never found a trace of him or his gang. And let me tell you, Ned, Spain isn't the sort to take chances of this kind without being sure of getting away with the goods, and hiding them and himself where no one is going to find him."

"I've got some news, too. Mr. Murston's coming down for the trial trip on Thursday."

"Good business!" exclaimed Ned. "Jolly old sportsman! I knew he would. Shall we be ready, Derry?"

"Rather! We could fly her to-day, for that matter. But I'm going to give her one more coat of dope. Then on Wednesday we shall fill her, and be ready for the first flight. I mean to take her up at dawn, Ned. We don't want a crowd. But don't let anyone know. Let 'em think she'll start at eight. That's the idea they have in the yard."

"You're right A crowd might be not only unpleasant, but dangerous. You may be quite sure Spain will have his spies around."

"Probably had them around all the time," returned Derry, more gravely. "And if it hadn't been for our barbed wire, and pass- words, and all the rest of our precautions, he'd have had one in the works. Let me tell you, I don't underrate the abilities of Mr. James Spain or of Mr. Cyprian Coyle."

"I wish we could think of some way of bottling the beggars," he said. "There's no safety or comfort in the airways so long as those fellows are abroad."

"We shall get them sooner or later," replied Derry, and, though he spoke very quietly, there was a ring of absolute certainty in his voice which impressed Ned strongly.

"I must go out into the yard, Ned. There's a lot to do to-day. You might go through the rest of those letters, and then join me."

All that day and the next the two young partners worked from early morning until late at night. They left nothing to chance, but personally inspected every bolt and nut, every yard of fabric, and more particularly the oil and petrol for the new engines.

Late on Wednesday evening Mr. Murston arrived. As usual, he had been working in London up to the last minute, and, strong as he was, he looked tired. With him came a quiet-looking middle- aged man with a dark, clever face and curiously bright eyes. Mr. Murston introduced him to the boys as Mr. Sebastian.

"He's a bit of an expert in aircraft," he told them, "and a very good friend of mine. I have promised him that he shall join us on our trial to-morrow morning."

Derry and Ned were a little surprised at having a total stranger sprung upon them in this fashion. But any friend of Mr. Murston was naturally theirs, and at supper that night Mr. Sebastian made himself so pleasant that they both took to him tremendously.

At nine Derry went out to have a last look round and see that his guards were all properly posted.

During the whole of the time that the Argonaut (as the new airship was called) had been under construction, no stranger had been allowed within sight of her. The enormous shed in which she was being built was as carefully guarded as a munition factory had been during the Great War.

A huge fence of barbed wire, highly charged with electricity, surrounded the whole of the works. This fence was double, and in the space between guards were posted day and night.

All turned in early, but it was a long time before Derry could get to sleep. He was so desperately anxious that the trial might be a success.

Everything he had in him, every ounce of skill and energy he had put into the Argonaut. He meant her to be a world beater, and it seemed to him that it would break his heart if she did not realise his hopes.

At last he slept, but at the very first whirr of his alarum, set for four o'clock, he was out of bed. A plunge in a big tub full of cold water cleared his head and braced his body. Then a cup of hot coffee with milk, but nothing to eat, and he was out in the yard, over-seeing the job of bringing the Argonaut out of her huge hangar.

Here the others joined him, and watched with breathless interest while the great, shining beauty emerged for the first time into the open. The newly risen sun, striking on her vast yellow envelope, turned her into a thing of gold, and the rays reflected from her shining metal work made these parts shine like silver.

"She's wonderful, Derry," said Mr. Murston, in his great, deep voice. "Beautiful lines! Upon my word, if she's as good as she looks, she'll lick creation!"

Mr. Sebastian was the only one of the party who did not speak. He never said a word, yet Derry, glancing at him, was conscious that he was intensely interested.

Presently they were all aboard, and with his heart beating faster than usual, Derry gave the signal to cast off.

Early as it was, some scores of people had collected outside the wire. They cheered as they saw the slim, yellow beauty rising from her cradle. Derry did not even hear. Through his telephone he gave the order for the engines to be started.

The words were hardly out of his mouth before there came a low, deep, purring hum, and instantly the big ship shot forward. Quickly and yet more quickly, but the sound, instead of increasing, diminished.

"Nearly so, sir," replied Derry; and spinning the wheel, sent the Argonaut circling in a swift curve.

It was a command, and Derry stared a moment at the stranger. Yet Mr. Sebastian did not seem to be conscious that he had said anything out of the way.

Derry obeyed. He rang for full power. The Argonaut shot away at an amazing speed; eighty miles an hour—ninety—a hundred! And still the revolutions increased until the gauge showed that she was cleaving the air at the amazing rate of 109 miles an hour.

Derry stood with his eyes fixed upon the face of the gauge. He could hardly believe his eyes.

Nearly 110 miles an hour, and this at first start before the engines had been run in.

A hand fell on his shoulder. It was Ned's. Derry turned and saw Ned's face with a curious expression upon it.

Derry looked. Two enormous biplanes were flying one on either side of the Argonaut, each about two miles away.

"What's it mean?" asked Ned. "They are Government craft—Handley-Pages. Why are they pacing us?"

CHAPTER XX. — MR. SEBASTIAN'S REAL NAME

DERRY stared at the two great 'planes. So silent were the engines of the Argonaut that the roar of their exhaust rattled across the sky. They kept station perfectly, but it was clear that they were going pretty well all out.

He turned to Mr. Sebastian, and found that gentleman regarding him with a grave smile on his clean-cut face.

"Yes, they are Royal Air Force, and are here for two reasons. But carry on. You shall hear all about it later."

"Pacing us, I suppose," whispered Derry to Ned. "I expect Mr. Murston has worked it. Independent observers, you know. In spite of what the papers say, there are some live people in the Government."

"She certainly is," agreed Derry heartily. "It's almost too good to be true. We ought to get another ten out of her when the engines are run in."

For the next ten minutes or so Derry kept the Argonaut travelling at full speed, at a height of about two thousand feet. Then Mr. Sebastian came close.

Again it was an order, and again Derry obeyed. Using the horizontal rudders he sent the long, slim craft lifting skywards. She shot upwards like a fish rising to the surface of a pond. The needle of the barograph went steadily round the dial, and as it rose so did the thermometer fall.

The big gondola or car was warmed by electric radiators. These were switched on, but even so it grew colder every minute.

At the ten thousand feet level a white rime began to condense upon the rigging, and at twelve this turned to real ice. Still she went up.

At fifteen thousand she was passing through thin, fleecy clouds. They were cirrus clouds, and composed of vapour in a frozen state. Inside the car everyone was shivering in overcoats. Everyone, that is, but Derry. He was too excited to feel cold.

"Yes, sir. And it's about as high as we can go. You see, we are using helium gas, not hydrogen. Hydrogen might give us an extra thousand feet, but helium is a deal safer."

"Not a yard, sir," replied Derry. "The ballonettes are made to expand like a concertina. They adjust themselves to the pressure, whatever the height."

"That is very ingenious. But the more I look at this craft of yours, the more I am struck by the number of novelties which I see on all sides. These engines seem to possess immense power, yet they are smaller and lighter than any that I have ever seen."

"They are my father's invention," explained Derry. "They are on quite a new principle. They are really gas turbines."

"Their silence is very wonderful, and altogether I consider the Argonaut an immense advance on any dirigible yet constructed. Your control, too, is amazingly simple. Was that your father's invention also?"

"H'm, I may have to ask you to seal that patent until His Majesty's Government experts have been into the matter. Now I think I have seen enough," he added. "Will you take her back again to her hangar. I have to leave for London almost at once."

"Why not let us take you there, sir," suggested Derry. "We can drop you at Hendon in about three-quarters of an hour."

"I had not thought of that," replied the other, smiling. "Very well. It will save me a good deal of time, and time is valuable to me these days. You had better let the two 'planes know, and they can wireless to have everything ready."

"I think our wireless installation is at least as good as theirs," replied Derry quietly. "Will you write out a message, and Sharpe, our wireless man, shall send it."

Mr. Sebastian wrote his message, then moved away and began to talk to Mr. Murston. Ned looked hard at him.

"I say, Derry," he remarked, "that chap behaves as if he owned the whole show. Who is he?"

"For me, too," agreed Ned. "I say, there's the big smoke in sight. We shall be at Hendon in another quarter of an hour."

As they came over Hendon the two Handley-Pages circled, then dived away towards Hounslow. Short as the notice had been, a number of men were ready down below. The Argonaut dropped quietly, and since there was no wind to speak of, was easily moored and made safe.

As Derry meant to go straight back he did not leave the car, but before he descended Mr. Sebastian came up to him.

"Holt," he said quietly, "I am very pleased with your airship in every particular. I am also greatly obliged to you for giving me the opportunity of so interesting a trip. Now I am going to return evil for good. I must inform you that, under powers conferred on me by the Act for the Defence of the Realm, I am going to requisition your ship for a special purpose."

Mr. Murston, who stood by, looked at him, and gave a low, deep chuckle, which Derry hardly noticed.

"Who are you?" he demanded of Mr. Sebastian. "What right have you to take our airship?"

"If I answer your first question, I give you the answer also to the second. I am Lord Meripit, and I have the honour to be His Majesty's Secretary of State for Home Affairs."

"So he is, Derry. At least, that's his family name, and he's got a perfect right to use it if he wants to."

"You must forgive me, Holt," cut in Lord Meripit. "I find it useful to travel incognito at times, and in this case I particularly wanted to see the trial just as an ordinary private person. Now, as to the purpose for which I am going to commandeer the Argonaut, I think it is one of which you and Barlow will approve. I want her to help in hunting down this scoundrelly pirate, Spain."

"To hunt Spain?" repeated Derry, his face lighting up. "Why, yes, sir—that is, my lord—of course you can have her for that."

"Of course I shall, Holt. I could imagine your feelings if I put someone else in command of your pet invention. Rest easy. Wherever she goes, you and Barlow can remain in charge. I understand from Mr. Murston that you have already had more than one encounter with this ruffian Spain or other members of his gang. Your experience may come in very useful in this respect."

"I only hope it will," replied Derry heartily. "There'll be no safety anywhere in the air while a fellow like that is loose. And Ned and I owe him one for burning our dear old Air Barge."

"Ah, Mr. Murston told me about that. Indeed, you were lucky to get off with your lives. The last exploit of Spain's—this robbing of the Northern Limited—has roused the whole country against him. We must run him down even if we have to mobilise the whole of the Air Force."

"It must have been Spain," replied Lord Meripit. "We now know definitely that the robbers escaped in an airship. She was seen going north."

"No," he answered, "unfortunately not. We are still quite in the dark as to the ruffian's haunt. And when you consider what huge areas there are in the Highlands of Scotland which are quite uninhabited and hardly known, and when you think of the hundreds of small islands off our northern coasts, you can realise that the work of locating this pirate's haunt is going to be no easy matter."

"Good!" Lord Meripit took out his watch and glanced at it. He frowned slightly. "Holt, I have an engagement in Downing Street in an hour's time. I can't wait to listen to you at present. Tell me, can your friend Barlow take the Argonaut back to Marchester?"

"Very well. Will you and Mr. Murston lunch with me at half- past one? Then we can talk this matter over, and afterwards I will send you back to Marchester by 'plane."

Lord Meripit hurried away, got quickly into the great car that was waiting for him, and went swirling off in a cloud of dust.

CHAPTER XXI. — DISGUISING THE DIRIGIBLE

IT was the first time that Derry had ever lunched with a Cabinet Minister, but the experience was a pleasant one.

The lunch itself was a very simple affair. There was some fish, a roast chicken, and a perfectly plain pudding. But this did not surprise Derry. Since his first meeting with Mr. Murston he had mixed with many rich folk, and had found that the more distinguished they were, the more simple, as a rule, were their tastes.

Lord Meripit waited until the meal was over, coffee had been brought in, and the butler had left the room. Then he lighted a cigarette and turned to Derry.

"It's—it's a very simple one, Lord Meripit," he answered, stammering a little. "But it might be worth trying if the R.A.F. craft can't find where Spain keeps his airship."

"I don't suppose for a moment that they will," said the Minister. "They tried hard enough after that attack on the Leviathan. There were at least a score of 'planes and a dozen blimps searching without success for the better part of a week. But they found nothing—absolutely nothing."

"Surely that's very odd?" put in Mr. Murston. "A hangar big enough to hold a large airship such as Spain's is a pretty conspicuous object."

"You forget," Lord Meripit reminded him, "the Germans hid one of their largest Zeppelin hangars under a market garden. Scores of our men flew over it without ever having an idea what was beneath. It was not until the big advance that the secret of the garden was discovered."

"Ah, then you think Spain has camouflaged his hiding-place in some similar fashion?"

"I am sure of it," returned the Home Secretary. "And unless we can spot him emerging or alighting there is very slight chance of discovering his haunt.

"You may be quite sure he won't risk that, my lord," said Derry. "He comes and goes by night."

"Just so—and on dark nights, too," was the answer. "Well now, Holt, let us hear your suggestion. I think you spoke of setting a trap?"

"That was my idea," said Derry modestly. "My notion was this—to camouflage the Argonaut as a cargo ship. We could change her colour and her shape without much trouble, and we could install a small aeroplane engine just to make a noise. Then we could advertise her to sail regularly on some particular route—say from Bradford or Sheffield to Glasgow. Sooner or later Spain will have a shy at her. Then we throw off our disguise and go for him."

"It is not a bad idea," allowed his host, "but I see one objection. Spain's spies, you may be quite sure, keep a sharp eye on your hangar at Marchester. They will see that the Argonaut is away, and that will arouse Spain's suspicions."

"I thought of that," said Derry. "We should have to put another dirigible in her place, one painted to resemble her. We could manage the substitution easily enough if we worked it at night."

"Yes, that can be done—it shall be done. I will see about it at once. As for you, Holt, you had best go back to Marchester and make arrangements. But don't touch your Argonaut for the present. She must be moved before she is made up for this new encounter."

Derry drove back to Hendon in state in Lord Meripit's own car, and returned to Marchester in the comfortably inclosed body of a very fine biplane.

The Argonaut, he found, had got back quite safely, and was locked away in her hangar. Ned was in the office, and there Derry and he sat together until supper time, discussing plans and drawing up specifications for the disguise of the Argonaut.

The very next day a letter arrived from Lord Meripit. He had already decided upon the dirigible which was to be exchanged for the Argonaut, and he told Derry of the hangar to which he was to bring his new airship. Derry, he added, had better come up to Chantry Magna, where this hangar stood, and supervise the disguise of the dirigible which was to represent the Argonaut.

With an unlimited number of workers at his disposal, Derry made things hum. Within a week the Changeling, as Derry called the Chantry airship, had been painted and altered until she looked the double of the Argonaut, and Derry had only to wait for a dark night to make the exchange.

He had not long to wait, for on the third day after the Changeling was ready came a dull evening with a threat of drizzle in the air. The glass, however, remained high, so there was no likelihood of wind.

About seven that evening, Derry, who had returned to Marchester, got a wireless from Lieutenant Hammond, the Government man in charge at Chantry, saying that the night seemed suitable, and, unless he heard to the contrary, he intended to start with the Changeling at midnight.

Derry, having translated this message from the cypher in which it was sent, read it to Ned.

"Yes, we couldn't have a better night for the job. By Jove, Derry, I do hope this plan of yours works! It'll be a bit of a feather in our caps if we nobble Master Spain."

"It isn't that I'm thinking of so much," replied Derry. "I'd let anyone have the honour and glory if only Spain were out of the way. What I'm keen about is to show the people in this country what an airship can do in the way of rapid transport. Once we can start carrying stuff with the Argonaut, we've got the 'planes absolutely whacked. But we can't do a thing until we've finished off this marauder."

"That's a fact, of course," allowed Ned, "and, like you, I'm for a quiet life. Still, I can't help rather looking forward to the big scrap. We've got a biggish bill against Spain, old son, and I want the satisfaction of putting 'Paid' to it."

"It ought not to be long before we get the chance," returned Derry. "We're going to work like beavers, once we get the Argonaut into her new quarters. Everything is ready there, and it should not take more than a week to disguise her. Poor dear! She'll look worse than the old Air Barge before I've finished with her."

"I think we can, but I'm not quite so sure about the men at Chantry. Hammond told me they were all right, but he doesn't know them personally, as you and I know our fellows."

It seemed a good idea, so they both turned in and got a sleep. It was just about twelve when Green roused them.

"All's ready, sir," he said. "But there isn't no hurry. We can do the trip twice as fast as that old Government 'bus."

Green's tone conveyed a lordly disdain for the Changeling. In his eyes there was only one airship worth talking about. That, of course, was the Argonaut.

They got aboard about half-past twelve. The drizzle had ceased, and though Marchester was shrouded in a thin mist, the weather seemed to be clearing.

"It will be quite clear above the thousand foot level," said Derry. "Not that it matters much, since they can't see us from the ground."

He was right. The Argonaut had not even reached five hundred feet before the stars became visible. At a thousand she was in clear air, with all the constellations gleaming like jewels overhead.

The moment her engines were started she shot off with her wonderful speed and silence. Derry, as usual, was at the controls. There was hardly a breath of wind, and a child could have steered the great ship. With her engines humming like monstrous tops, she rushed through the calm night.

"Keep an eye lifting for the Changeling, Ned. We ought to pass her pretty soon."

"It's even chances whether we see her at all," Ned answered. "Like us, she's running without lights. Foolishness, I call it. We might have run whack into one another if it were really a thick night."

At that moment the door of the car was flung open, and Wilfred Sharpe, the wireless operator, came plunging in. He was a tall, thin young fellow, with a keen, clever face—a face which now was white, while his dark eyes flashed with excitement.

"There's something attacking the other ship, Mr. Holt," he cried in a strangled voice, "It's Spain. He's shot away her rudder and her aft propeller. She's helpless!"

"Spain!" cried Derry and Ned in one breath. "Who is the message from—Hammond?"

"No. It's from Mr. Murston himself. It seems he's aboard, making the trip to Marchester."

"Mr Murston aboard the Changeling! Oh, my goodness. Ned, what could have induced him to do such a crazy thing?" He swung round on Sharpe. "Why are you not at your post? Why aren't you taking the rest of the message?"

"Because it's stopped. Their aerial has been shot away, or perhaps the whole ship has crashed. I called and called, but no more came through."

CHAPTER XXII. — IN TOUCH WITH THE ENEMY

"CRASHED!" gasped Derry. "Then they have either got Mr. Murston or killed him. Where did this happen, Sharpe? Did they tell you?"

"If we had only started a few minutes earlier, Ned!" he said. "We're not twenty miles away."

"We may still get there in time," cried Ned, and flinging himself through the door of the car, was gone.

His action brought Derry to his senses. He sprang to the telephone, and called to Green for "Full speed!" Then, studying his map, he slightly altered the course of the Argonaut.

At once the pace of the airship began to increase. She had been running at an easy eighty. Now the deep humming of the engines rose a note, and the dial of the speedometer showed that the number of revolutions was climbing. Within a very few minutes the hundred-mile mark had been reached. And still the needle crawled upwards until the long, fish-like fabric was darting through the air at a speed of nearly two miles a minute.

"I can see the lights of Reading," he began. "The Thames is almost under us. We shall be over Peppard in less than five minutes. I have two men out on the cat-walk, watching."

Busy with his navigation, Derry could only carry on and trust to his look-outs for news. He had not long to wait.

"A point north, sir," came a voice. "I can see something a- flashing from that direction."

Derry obeyed. There was a short pause. Then the voice again through the telephone.

"I was right, sir. There's a chap Morse-coding with a flash lamp. Slack speed, and I can get him."

With his heart beating hard, Derry rang off the engines, and as their deep hum ceased, sprang to the window and looked down.

The Argonaut was floating in still air at a height of about a thousand feet above the quiet down lands which lie to the north of Peppard Common, in Oxfordshire. It was clear now, and sure enough, from a hill-top below, someone with an electric torch was signalling with great vigour.

Dot-dash. To Derry the Morse code was as familiar as A.B.C., and at once he caught the sense of the message from the ground.

"This is Hammond, of the RX 19. (RX 19 was the official number of the Changeling.) Attacked by Spain. Driver down. He has Murston prisoner."

The last flash had hardly flickered into darkness before Derry was at his telephone again.

"Full speed, Green. Spain's only five minutes ahead. With any luck, we'll catch him!"

His answer was the whirr of the engines as they instantly broke into life again.

But Derry never saw the message. He was feverishly setting the Argonaut on her new course, and at the same time sending her rapidly upwards. The higher they flew, within reason, the better chance there was of spotting the pirate craft.

"Yes, of course, Ned," he said. "Spain was only five minutes ahead of us. Do you realise what that means?"

"Of course, we are armed. But what use can we make of our arms? Don't you realise that Mr. Murston is aboard?"

Ned's jaw dropped. A look of the most complete dismay crossed his big, handsome face.

"But Spain did, Ned. That's one reason why he risked stopping to pick him up, for he must have known that we were not far away. Ned, he's got us in the hollow of his hand. We can't even fight him, and once he has got Mr. Murston safe in this unknown hiding- place of his, he's got something to bargain with."

"You're right, Derry. Spain certainly has got the whip-hand of us this time." Then his face cleared a little. "But, see here, Derry. What about trying to shoot away his steering-gear? We're so much faster than he that I should think we might do that without risking hitting the cars."

"Yes," agreed Derry. "It's just possible we might be able to do that. But you must remember that we shall need to get pretty close to manage that and that Spain probably carries more and better guns than we. You see, we are not armed as we should have been in another week's time."

"It's a ghastly mix-up," said Ned, frowning. "Still, we must do our best. I only wish to goodness that the boss had never taken this crazy freak into his head. What on earth did he want to take this trip for?"

"It's no use blaming him," replied Derry. "He's mad on airships ever since we took him for his first trip in the Air Barge. He has been going up in every sort of craft. Why, he's been to Paris with the Airco people at least half a dozen times."

"A point farther west, Derry. She's only about three miles off, but flying very high. Here, I'll go up to the observation post, and let you know exactly how to steer."

He was off again, but presently his directions came dropping through the 'phone.

"I can see her quite plainly against the stars. You're half a point too far west. Yes, that's right now; but you'll have to rise a lot. She's climbing all the time."

Using his lateral rudders, Derry sent the Argonaut climbing skywards. Green and his men, he realised, were getting every ounce possible out of the engines, for the indicated speed had risen to over a hundred and sixteen miles an hour. Beneath them, Oxfordshire swept away like a star-lit dream.

"We're gaining, Derry," came Ned's voice again, "but he's still above us. I'd no idea he could climb like this. He's whacking her up, too. His engines aren't so much behind ours."

"I've done that long ago. But we can't start shooting yet awhile. I tell you it's getting cold up here."

Derry knew that was true. Even in the warmed shelter of the car the temperature was not far above freezing-point. Up there at the observation post, in the full rush of the parted air, the cold must, he knew, be almost intolerable.

Minutes passed. Every now and then came Ned's voice, giving some slight change of direction. The Argonaut was above the 10,000 foot level, but Spain's craft was even higher.

On and on they drove. Then to Derry's straining ears came a faint crackling sound resembling that of electric sparks leaping from a charged Leyden jar.

"She's firing from her stern gun," was Ned's information. "And she's still above us, Derry. We shall have to swing out and climb."

Derry said something sharply beneath his breath. But he did as Ned had suggested, swung to the left in a semicircle, and climbed again.

Both these operations meant loss of distance, and by the time the Argonaut had reached eleven thousand, the pirate craft had a considerable lead again.

But the Argonaut had the speed, and soon caught up. Again came the crackle of Spain's machine-gun.

"It's no use, Derry," said Ned, in an irritated voice. "I'd no idea he could climb like this."

"I wouldn't. See here. Let's carry on till dawn. It'll be light up here in little more than an hour. Then we shall have a better chance of tackling him."

"That sounds good. But what about the weather? By the chart, there was a depression over the north yesterday. If we run into cloud, we're done."

"Not a sign of it at present," replied Ned. "Sky's as clear as a bit of window-glass. And anyhow, Derry, we haven't much choice. We can't shoot back so long as we're astern, and we must have light if we want to manoeuvre above her."

Derry saw that this was true, and agreed. He ordered Green to ease off a little, and they carried on, keeping at the same elevation, and just out of gunshot of the pirate.

So another hour passed, then the stars began to dim a trifle, and far in the east a faint pinkish glow appeared.

All this time they had been running almost due north, and, though the country below was still wrapped in the shadow of night, Derry knew that they must be over Yorkshire. He called Ned to come down and take over the navigation.

Ned, more than half frozen, was only too glad of the change. Derry gave him some hot coffee from a thermos flask, and had some himself.

"Any sign of help?" asked Derry. "We ought to have had an answer to our wireless calls by now."

"Not a ghost of a 'plane," said Ned. "If you ask me, Spain has been jamming our wireless. We've got to do the job ourselves, old son."

"I don't know that I'm sorry," he answered. "If it wasn't for Mr. Murston being in Spain's hands, I'd be glad. Hullo!" he broke off. "There's the telephone again. I wonder what we're going to hear now. Well, what is it?" he asked.

This time it was the voice of Haynes, the man whom Ned had left on the look-out.

"Enemy in plain sight, sir," he announced. "Two mile ahead, and about a thousand feet above us."

CHAPTER XXIII. — THE UTTERMOST HEIGHT

EVEN though the Argonaut was not travelling at full speed, the blast which met Derry as he reached the forward observation post nearly took his breath. In spite of his helmet and goggles, and thick leather coat, his eyes streamed, and the freezing air bit to the bone of him.

But he had other things to think of besides mere bodily discomfort, and, anyhow, he was well used to this sort of thing. His eyes were fixed at once on the long, slim shape of Spain's craft flying high above the Argonaut, and cleaving her way straight northwards.

Though the sun was not yet above the rim of the horizon, there was plenty of light to see her, and a beautiful sight she was, with the pink glow of dawn upon her pale-coloured fabric, and her great screws spinning dizzily, making whirling circles of light.

Derry stared at her eagerly, yet in his heart was no triumph, but rather deep anxiety. Here was what he had longed for during months of hard and patient work—to be within reach of his enemy in an airship of his own design and building. He believed that he could rise over her and smash her as easily as Spain himself had smashed and sunk the old Air Barge.

To crash the pirate ship meant the death of Mr. Murston. This was unthinkable, for not only was Mr. Murston's life of immense value to very many people and to the tremendous business of which he was head, but also Derry had grown to love him almost like a father.

He saw clearly that Ned's plan was the only possible one. The Argonaut must rise high above the pirate, and having got the gauge of her, must endeavour to destroy her rudders.

If that could be done, the pirate would be helpless, and might be forced to surrender.

Yet Derry could not conceal from himself that it was going to be a desperately difficult business. While he and his men would have to concentrate their fire on one particular portion of the pirate, Spain, for his part, could rake the whole of the Argonaut.

And though, owing to the fact that their ballonettes were filled with non-inflammable helium gas, he could not set fire to them, yet it was quite likely that he might damage or disable them.

But it was no use thinking of unpleasant possibilities. The thing was to get to business as quickly as might be, and, turning to the telephone, he gave Ned the word to rise.

Instantly the Argonaut's bow cocked upwards, and she began to climb. Up she went at a long, steady slant, her stem still pointed exactly for the stern of Spain's ship. She gained rapidly, and every minute drew nearer to the level at which Spain was flying.

But Spain's people speedily noticed the manoeuvre, and the pirate, too, tilted her bows and slanted upwards. But her engines had not the driving power of Derry's, and she lost way at once.

Derry saw tiny sparks of red fire glow out from her after-gun platform, and there was a crackling sound which in this thin air was hardly louder than tearing paper.

With ugly, hissing sounds machine-gun bullets came spraying past Derry's ears, some ripping harshly through the fabric of the long slim body of the airship.

Derry played his trump card. He shouted down to release ballast. From below came a sharp hissing sound, and looking back he could see a faint mist of water spray vanishing like smoke in the trail of the ship.

At once the Argonaut began to rise vertically, and in a flash she was level with her opponent.

Spain saw his danger, and copied Derry's tactics. Out streamed the contents of his ballast tanks, and up he shot, at an even more rapid speed than the Argonaut.

All the time he kept his machine-gun going, and Derry, who could not return his fire for fear of hitting Mr. Murston, was forced to slacken speed until he was a mile behind the pirate.

The sun was up now. The heavens were rosy-gold, and twelve thousand feet above the earth the two great dirigibles fought for height.

Up and up they rose into those tremendous spaces where the air is so thin that man gasps for breath, panting to get sufficient oxygen into his labouring lungs. The blood sang in Derry's head. They had no oxygen apparatus aboard, and it was in Derry's mind that, if Spain had, it must give him a great advantage.

"Then empty the other," answered Derry. "We've got to beat him at his own game."

Away streamed the contents of the second tank, and up went the Argonaut. The cold was terrible. The temperature was below zero. But in his intense excitement Derry hardly noticed this.

"Fifteen thousand!" cried Ned, through the telephone. "Aren't we above him yet?"

"It looks as if he'd emptied his tanks," replied Derry. "There's no more water coming from them."

"He's chucking furniture overboard, by the look of it, sir," said Haynes, the man who was standing alongside Derry at the look-out.

Sure enough, some bulky object shot down from the central gondola of Spain's ship, and vanished into the abyss below. It looked like a table.

"Green says the second tank is empty. We've reached the ceiling, so far as we are concerned."

"No; we're running out of petrol as it is. We didn't fill up all the tanks, as it was only for a short flight. Green says we haven't more than enough for another hour at full speed."

Derry groaned. He had not thought of this. "It's now or never, then," he answered. "I'm going to try to pass her, and come back on her."

By Derry's direction, Ned steered away to the right, and again the Argonaut was driven at the very top of her speed. She gained rapidly, so far as pace was concerned, but Spain still remained several hundred feet above her.

"It's the hydrogen," explained Derry to Haynes. "Gives him a bigger lift than our helium."

Haynes did not answer. Derry, looking at the man, saw that he was blue in the face, and near to choking. No wonder, for they were now two thousand feet higher than the top of Mont Blanc, and to the thinness of the air had to be added the bitter intensity of the cold.

In spite of what Ned had said about the Argonaut having reached the limit of her lift, she was still ascending slightly—climbing by sheer engine power alone. Derry's spirits rose a little. He was almost on terms with the enemy. Another couple of hundred feet and he would be above her.

Then, while he watched, suddenly a rain of all sorts of objects began to fall from Spain's ship. Boxes and bales, kegs of oil, cases of food—these and other things streamed earthwards. Spain, realising his plight, was jettisoning cargo wholesale.

Up leapt his ship—up to a height which certainly no dirigible had ever before reached, and one which the Argonaut could never hope to emulate.

CHAPTER XXIV. — THE END OF THE CHASE

FOR the moment Derry was on the verge of despair. To be so near to his enemy, to have him almost in his clutches, yet to be absolutely unable to reach or harm him, was the most maddening experience he had ever had, and he stood there at the look-out, glaring up at Spain's ship, heedless of the cruel cold or the bite of the frozen air that screamed past him.

But Derry was never one to give way completely. Presently he turned to the telephone again.

"Ned, Spain has jettisoned half his cargo. He's risen another thousand. There's not a dog's chance of our reaching him. But, listen. We must follow him. If we can do that, and find where he hangs out, we shall get him sooner or later."

"You forget, Derry," grunted Ned in a very downcast tone. "We've petrol for less than another hour."

"I had forgotten, Ned. I'd quite forgotten. This is simply awful. What on earth can we do?"

"Carry on as long as we can," Ned answered gloomily. "Carry on, and trust to luck. But even if we had the petrol, you may take it as one sure thing that Spain wouldn't drop to his hangar so long as we had him in sight. He'd take us to the North Pole first."

"I suppose his petrol is limited, like ours," growled back Derry. "Can't we get any help?"

"Not while we're so close to him. We've been doing all we know to call up help, but the beggar has managed to jam our wireless all the way through."

Derry was silent. There seemed nothing more to say. Again he stood staring up at the long, slim shape outlined against the cold blue overhead. Her engines were roaring full blast, and she was travelling at the top of her speed towards her unknown destination in the far north.

Then he looked down. Half Scotland lay stretched beneath him. From this enormous height he could see mountain chains like caterpillars, great lakes like ponds, and could actually glimpse the North Sea and the Atlantic at one and the same time.

Almost exactly underneath was a thin blue riband widening here and there, and cutting all across the breadth of land. It was the Caledonian Canal. To the north, and slightly to the west, was a patch of white which was the summit of Ben Nevis. Still farther north lay the rugged tangle of the Highlands, mountains, moors, deer forests, bright under the glow of the summer sun.

Miles upon miles of the wildest and least inhabited country in the British Isles, and away to the west islands big and little—hundreds of them.

Derry's heart sank again as he thought how many hiding places there must be in all those little known wastes.

Overhead the sun shone brilliantly. East, west, and south the air was clear as crystal, but in the extreme north a faint grey mist obscured the horizon. There was fog up there, and it was for the cover of it that Spain drove confidently forward.

Yes, that was how Spain had come to venture on this raid. He must have known that fog was brewing, and that it would hide him, on his return, from the eyes of any who pursued him.

Derry racked his brains for some way of closing with the enemy, but racked them in vain. It was flatly out of the question for the Argonaut to reach the height at which Spain's corsair craft was flying.

"See here, Derry," he said. "If we have to come down in the middle of a deer forest, it's ten to one we shall lose the Argonaut and with her the best weapon we've got against Spain. Take my tip, and let's get to Cromarty while we can."

Next moment the Argonaut's pointed stem swung to the east, and she went shooting towards Cromarty, dropping rapidly as she went.

Derry glanced once more at the long, slim shape of Spain's craft high against the sunlit sky, then, with thoughts too bitter for words, turned and came down the ladder.

Later that afternoon Derry and Ned sat together in a room which had been assigned to them by the officer in charge at Cromarty.

An excellent lunch had been served to them, but in spite of their long journey and all that they had done during the past twelve hours, neither had eaten much.

Derry sat in his chair, with his elbows on the table, his chin on his hands, and such a dejected look on his face as went to Ned's heart.

"Cheer up, old son!" said Ned at last. "We've been through some tough times and come out on top. We'll do it again."

"I wish I could think so," Derry answered. "But I don't see any way out of this. The worst of it is that it's all my fault. It was I who proposed this fool trick of dressing up the Changeling."

"And you who suggested to Mr. Murston that he should take the trip in her, I suppose?" said Ned drily. "Don't be an ass, Derry. To put it quite plainly, dear old Murston has no one but himself to thank for the fix he's in. For that matter, he'd be the first to own it."

"Spain's got him, anyhow. That's all there is to it. And how we're ever to get him out of that ruffian's clutches is more than I can say."

"We must find Spain's lair. That's the only thing to do," declared Ned. "To-morrow we'll take the Argonaut and jolly well search the whole country. As I've said before, you can't hide a dirigible like you would a motor-car.

"And see here, Derry," he went on more quietly, "There's another point to be considered. Spain must have built his airship somewhere, and he must have had a lot of men to help him on a job like that. If we could find where he did the construction work, it would be a step in the right direction."

"I've thought of that," Derry replied. "But I expect he built her in the same place as he keeps her. And that must be amazingly well hidden."

"Wait a minute," said Ned quickly. "I've thought of something else. Spain can't run a big craft like that without tons of petrol. Where does he get it from, and how does he get it to his den?"

"That's a good point, Ned. He must either have huge stores or he must be getting the stuff steadily. Yes—" He stopped short, "Those tins—those tins he chucked over this morning. I'd quite forgotten. They must have marks on them."

"You've hit it, Derry. You've got a bull's-eye this time. Come on. Let's go and find them."

He snatched up his hat and rushed out. Derry followed. They went straight to the commandant, and two minutes' explanation resulted in the production of a powerful touring car. A hamper of food was put into the tonneau, the commandant himself supplied the boys with a first-rate map, and away they went at such a speed as would have put terror into the soul of anyone but an airman.

It was a matter of something like sixty miles to the spot where Spain had made that last big bid of his for superior height. Derry, with his trained eye, had noted the spot—noted it, that is, as well as anyone can note a spot from an airship travelling at something like three miles above earth's surface.

"There wasn't any water very near. That's one thing I'm sure of," he said to Ned.

"Were there any houses?" asked Ned. "If a parcel of kids have been grubbing around in the débris, it'll be just as bad as if they'd fallen in a lake."

"Didn't see any houses," responded Derry, as he changed down to second on a long, steep climb.

"But the things may have lodged on top of some beastly mountain or dropped down a crevasse. You never can tell," said Ned.

"Who's croaking now?" snapped Derry. "It was open moor with a road running north and south across it. A main road, for there were telegraph wires. And there was one house with a good-sized garden, about a mile off the road to the west with a drive running from the road. Another thing I remember is a small hill with a clump of firs on the top."

"You're a bit of a wonder, old son. I'd never have spotted all that. Wait now. I'll study the map a bit, and see if I can find anything that answers to your description."

There was silence for two or three minutes, then, as the car reached the top of the hill, Ned plumped a big forefinger on a spot on the map.

It was not much after four when they reached the spot in question. Everything answered exactly to what Derry had described. But as they drove down that long, white road the extent of the moor appalled them.

"It'd take a month to search this," groaned Derry. "And from above it didn't look bigger than a ten-acre field."

A moment later a heavy, middle-aged gentleman in rough tweeds and big boots strode out. He had a large, red face, and seemed to be extremely annoyed.

CHAPTER XXV. — THE CLUE

"WHAT!" he exclaimed. "Are you the young scoundrels who nearly killed my keeper this morning, and who littered up a mile of my ground by dumping overboard the contents of your filthy flying ship?"

"You let me talk," he whispered. "No, sir," he said, speaking in as conciliatory a tone as possible. "That was the air pirate Spain, of whom you may have heard. We were chasing him, and in order to get away from us he jettisoned his cargo. We have come to you, sir, to ask for your assistance in the matter. We think that, if we can find some of the material he dropped, it may give us a clue to his hiding-place. Then we may be able to smoke him out."

"Why, of course I'll help you. A fellow like that ought to be hung. One of his tins fell within six feet of Macallum, my head keeper. Thick as his skull is, it would have smashed it if it had hit him. Here, you come in, you two. Come in and have some tea while I ring up my gillies. They're all on the telephone."

"Rather! He knows just where the stuff fell," replied Derry. "I say, Ned, I believe I feel equal to some tea."

It was a tea, too. Their host, Mr. Angus Maclaine, had truly Scottish views on the subject of hospitality, and besides hot bannocks and fresh butter, there were rowan jam, shortbreads, and about six different sorts of cake.

Mr. Maclaine himself poured out tea, and was really pleased at the way his guests tucked into the good things. By the time the meal was over, the gillies were on the spot.

"Now," said the big man, "I'll take you straight to the place, and it'll be a pity if you can't find something by which to identify this piratical person. The scoundrel has dumped enough stuff on my grouse moor to fill a furniture van."

It was not quite five when the party started out, and they had a good three hours of daylight before them. Macullum, the head keeper, conducted them. He was a thick-shouldered, powerfully- built Highlander, and though at first inclined to be rather silent and surly, soon thawed. Few people could resist Derry when he laid himself out to talk.

It was beautiful country, and late in the day as it was the sun still shone brightly. The air had the keen tang of the Scottish highlands, and there was a pleasant scent of peat and heather.

Derry thought that this was just as well, for the pace the keeper set was a pretty stiff one, and Derry was not as fresh as he would have been if he had spent the night in bed.

They crossed a ridge, and dropped into a wide valley beyond. Macullum pointed to a burn which came pouring down from the hills to the right in a series of white falls.

They quickened their pace, and as they came down the slope Derry saw a glint of light among the heather. It was the sun's rays reflected from some metal object. He ran forward.

It was a gallon oil tin flattened out as though it had been under a steam hammer. The two boys examined it closely.

The party scattered, and set to searching. Since Spain's airship had been travelling at nearly ninety miles an hour, the jettisoned cargo lay over a wide expanse of country. Still, they had plenty of searchers, and soon a considerable pile of stuff was gathered and laid on a flat rock by the burn.

Falling as they had from such a terrific height, the various articles were smashed and flattened in the most extraordinary fashion. Many of them were not recognisable, and as for any traces of their origin, there was nothing of the sort.

It soon became clear that Spain had foreseen this contingency, and that he had been careful to have all marks erased from everything used in his airship.

For more than an hour Derry and Ned patiently and carefully examined everything that the gillies brought up, and at the end of that time the result was absolutely nil.

"It does seem as if Spain was a bit too cute for us," growled Ned, as he flung aside a piece of broken woodwork. "But we won't give up just yet, old son. Let's take a walk round ourselves, while there's still light."

"I don't think it's much good," said Derry despondently; but, all the same, he got up and followed Ned.

Ned led the way across the burn. Derry, just behind him, was jumping from one rock to another when his quick eyes were caught by a little patch of white in a clump of fern on the steep bank.

He swooped upon it, and found it was a piece of paper crumpled around some hard object, and held together by an elastic band.

His fingers shook a little as he pulled off the band and carefully unfolded the paper.

Derry smoothed out the paper with the greatest care. It was a leaf from a note-book, and on it were a few lines hastily scribbled in pencil. Derry read them out:

"Taking my chance to drop this while the pirates are busy chucking stuff overboard. I was a fool to come, but that can't be helped. Been trying to discover where they are taking me, but only clue is mention by one man of lead mine. Wish could tell you boys to shoot and chance it, but—"

"Suppose he saw that someone was watching him," said Ned. "But it's a clue, Derry. A lead mine. There can't be many, especially in the north here."

"It's a clue, a good one!" he cried. "We must go back to Cromarty, Ned, and get the proper maps. Then we can start."

"We have," Derry answered. "Now we must go back at once. We must return to Cromarty to-night."

Mr. Maclaine was really distressed to hear that the boys would not stay the night. But on that point Derry was firm, and at seven the two said good-bye, and started on their long drive back.

Tired as they were, they were too excited to feel it, and at a little before ten the big car was back in its garage, and the boys in deep consultation with Captain Carson.

But the maps which he had were not sufficient, and it was necessary to telegraph to Edinburgh for fresh ones.

So the boys, tired out, went to bed, and in spite of all their worries, slept soundly enough.

They breakfasted with Captain Carson, who told them that the maps were being sent by special messenger, and would arrive about mid-day.

"The whole country is stirred up," he added. "The row about the robbing of the mail train is nothing to the excitement this business has caused. If Spain had captured the Prime Minister himself, there could not have been a bigger fuss."

All that morning the boys wandered restlessly about. At last, just before lunch, the messenger with the maps arrived in a big racing car.

The boys flung themselves upon them. The one they wanted was the large scale geological map showing all mineral deposits and mines.

"Here we are," he said breathlessly. "Here's the only lead deposit on the north coast. Ard-na-lish is the name of the place."

CHAPTER XXVI. — THE MINE MOUTH

"ARD-NA-LISH!" repeated Ned. "Yes, and here we are—old workings. So there's been a mine there at one time or another. I say, Derry, do you think Spain could have hollowed out the old mine and hidden his airship underground?"

"Hardly possible, Ned. And yet—" He paused, frowning. "Don't be too sanguine, old chap. We don't know that this is the place. Remember, Mr. Murston only heard a mention of a lead mine. It doesn't follow that it actually has anything to do with Spain or his lair."

"Nonsense!" he said. "The whole thing fits too well. Look at this place Ard-na-lish, right up on the coast of Sutherland, miles from anywhere, and the one spot in the whole of the north of Scotland where there is any lead. Depend on it that Spain has something to do with it."

"He may have something to do with it," allowed Derry; "but it doesn't follow in the least that Ard-na-lish is where he keeps his ship or ships."

"Why?" he asked. "What can you and I alone do against Spain's crowd? We can't get Mr. Murston out of their clutches."

"I don't suppose we can," Derry replied drily. "My idea is that we must first find where he is shut up."

"See here, Ned," he went on, "suppose we go and tell Carson that we think we know where Spain hangs out, or that we wire the news to Lord Meripit; within a few hours we should have half the Air Fleet buzzing over Ard-na-lish. Even if Spain is there, you may be jolly sure he can protect himself. He is probably quite able to hold his own against odds. Besides that, he has Mr. Murston as his trump card. He can treat him as the Germans did their prisoners—put him up in the line of fire, and defy our people to bomb him."

"I see," cut in Ned quickly. "I quite understand what you're after, Derry. You mean that you and I had better go up there on the quiet and see how the land lies. Isn't that the idea?"

"That's it, Ned. We'll not take the Argonaut, or even a car. We must disguise ourselves as crofters or fishermen. Then, if we can only find out that Spain is there or thereabouts, we can make up our minds what to do next."

"That's the ticket, Derry. I should say we'd best get up as fishermen. We should be less liable to attract attention, and we can both handle a boat. Come on; the sooner we start, the better."

They had to take Captain Carson into their confidence after all, for it was only through him that they could get the necessary disguises, boat, etc.

At first he was against their idea, and wanted to send a number of men up in fast cars. But Derry put the whole thing before him, and at last he rather reluctantly allowed that Derry's plan was the best. But he gave them a time limit, and told them that if he were without news of them at any time for forty-eight hours, he should at once send help.

Early next morning the two were off. They were to drive in a car as far as a place called Kilbridden, and there find a boat in which they could sail on to Ard-na-lish.

Luck was with them, in so far that it was a very fine day, and when they arrived at Kilbridden, they found there was a south- easterly breeze just enough to take them comfortably up the coast.

The boat provided was simply a biggish dinghy, with a main and fore sail. She was small enough for one man to manage, yet large enough to stand a fair amount of weather.

Their kit, too, was ready for them, and by the time they had changed into it and slightly darkened their faces, no one would have recognised the two smart young airmen in the pair of blue- jerseyed, sea-booted fisher-boys who got aboard the dinghy.

The Sutherland coast is rough and rugged, and anything but safe for those who do not know it. But they had a navigator ready in the shape of David Hulme, a middle-aged man who had served for many years in the Royal Naval Reserve, and who knew these seas like the palm of his hand. He was a stolid, silent Scot, but Derry liked the look of him, and felt sure that—whatever happened—he would be very unlikely to lose his head or do anything foolish.

Barring what he had read in the newspapers, Hulme had not seen or heard anything of the air pirate, and Derry's hopes sank very low. It did not seem to him possible that those who lived so near could have been completely ignorant of Spain's doings, if Spain really were anywhere on the coast.

"Remember," he said, "that a peregrine falcon never raids anywhere near to its roost."

Early in the afternoon they sighted a tall headland which, Hulme told them, guarded one horn of Ard-na-lish Bay. He said that the old lead workings were a little way inland, near the head of the bay.

Derry decided that it would be wise to land a little way down the coast, and explore afoot, so they ran into a tiny cove, and leaving Hulme with the boat, climbed the cliff, and walked across a wild stretch of moorland behind. They went very carefully, but did not see a single soul, or any live thing, except a few sheep and grouse.

Reaching the top of a ridge, they came in sight of the bay, and lay down in the heather to study the lie of the land.

The bay was narrow, and its mouth almost blocked by a small island, or, rather, a large rock. This rock rose about a hundred and fifty feet out of the sea, with sides that looked too steep for a goat to climb. The top, about three acres in extent, was flat, and covered with turf, and against the green of the grass were several small, dark objects.

"Yes, it can't be so inaccessible as it looks from here. But I say, Derry, where are these lead workings?"

"There! See that scar on the hillside, just inland from the head of the bay? That's the place; depend on it."

"Not now; we should be in full sight of anyone who happened to be about. We must wait till night, Ned."

"I don't agree with you," answered Ned. "We should probably get bogged or lost if we came messing around here at night. I suggest that we should walk inland, get round at the back of that big hill, and come out above the workings. The heather is at least a yard high there. It will give us heaps of cover."

"Right you are, Ned," he said. "We'll try it. But it's going to be a tough bit of stalking."

In this Derry was right, It took two hours' solid hard work to reach Ned's vantage ground. Much of the journey was done on hands and knees. At last they found themselves on top of the hill, where they lay flat on their stomachs in the heather, and peered down from an immense height into a wild glen below.

The country was desolate beyond words. Barring a few sheep, and a big golden eagle which hovered high in the blue overhead, there was not a living thing in sight. And the worst of it was that, from this lofty perch, they could see nothing at all of the entrance to the lead mines below.

"We'll have to go on a bit farther," he remarked. "See that big crag projecting out over the glen? If we climb out on that, we can get a good view up and down the glen."

"If there's anyone in the glen they'll get an equally good view of us," he answered drily. "But we'll try it."

More creeping and crawling, and at last they reached the crag. It was a huge shelf of rock projecting quite thirty feet from the summit of the rugged cliff. Some stunted birch trees grew upon it, and these gave a little cover.

Presently the two were stretched on its rim gazing down into empty space beneath. The silence was so intense that they could plainly hear the bubbling and purling of the little brook that ran down the centre of the glen a good three hundred feet below.

"That's better!" gasped Ned, with a sigh of relief. "Look, Derry! There's a hole near the base of the cliff. That's the adit. By Jove, yes, there's been someone there lately. There's a regular path."

A man came out of the adit. He was tall and lean, and wore rough overalls stained with mud. As he came out, he turned and looked up the glen, then down. His face, raised to the light, was keen as a hawk's.

Apparently satisfied, he set off walking briskly westwards in the direction of the sea.

CHAPTER XXVII. — THE MAN WHO VANISHED

"You can see that with half an eye," replied Ned. "What's to be done, Derry? Shall we wait till he's out of sight, then go and have a look at the workings?"

"Not much! Our game is to follow him and see where he goes. The workings won't run away. We can look at them any time."

Ned nodded, and drew back from the edge of the crag. In the deep stillness of the lonely place they could hear every footstep of the stranger as he passed almost exactly beneath them. They waited until he had got well on, then crept back to the cliff top, and began to work down it. They kept well out of view, and some little way behind the mysterious miner.

From this spot it was about a mile to the seaward end of the glen, where the brook tumbled across a narrow belt of shingle into the upper end of Ard-na-lish Bay.

The bay itself looked more like an inland loch than a branch of the sea, for its opening was almost entirely blocked by the island, and the deep dark water was smooth as glass.

The boys, however, had no eyes for anything but the man. They watched him cross the shingle; then he turned in to the right under the cliff on which they stood, and disappeared completely.

They crouched down and waited. The delay was not long. In about five minutes the man appeared again, and this time he was carrying a collapsible boat. It was one of those canvas arrangements with air tubes along the sides. They weigh only about twenty pounds, and will carry two men.

He walked into the water knee-deep, set the boat down, got into it, and began paddling away straight down the bay.

"Because that boat wouldn't stand any lop at all. He couldn't take her outside."

"By Jove, I believe you're right. But the island! What can he do there? He can't land. It's sheer cliff all round."

"It looks like it," replied Derry, "but all the same, its pretty certain there's a landing-place of some sort. Watch, now!"

Watch they did. Both felt as if they were on the edge of some big discovery, and their hearts beat more rapidly than usual.

The long man paddled swiftly across the placid surface of the bay, then, turning slightly to the left, vanished, boat and all, beneath the towering cliff. They waited. There was not a sound. He had disappeared completely.

Derry crawled back from the edge of the cliff, he reached the heather, and bending double, ran quickly towards the sea. Ned followed. They passed the island, and came out on to the northern horn of the bay.

The mouth of the bay was empty. The evening sun sparkled on the little waves, but there was no boat in sight, no sign of life, except gulls and the little black Highland cattle which grazed upon the summit of the cliff-girt island.

"He's there," he exclaimed, "and if you ask me, Spain is there, too. Ned, we're going to find our way to that island before we're many hours older."

It was a terribly long tramp back to the spot where they had left Hulme and the dinghy, and it was dusk by the time they reached it. Derry told Hulme what they had found; all he said was:

It was not safe to light a fire. The smoke might be seen. But they had a spirit stove, and Hulme made tea. There was plenty of cold food in the hamper, and they made a good meal. Then each rolled up in a rug and went to sleep.

To Derry it seemed barely five minutes before Hulme roused him. As a matter of fact, he and Ned had had a good four hours' nap, and both felt much refreshed.

The night was calm and fine, but a little mist hung over the sea. This was all the better for their purpose, and they were soon afloat, and, with row-locks carefully muffled, pulling for the mouth of Ard-na-lish Bay.

The distance was nothing by water, and they were there in less than an hour. Rounding the point of cliff which ran out to the south, they found themselves close under the towering crags of the island.

They paused, hanging on their oars, straining their eyes for any sight, and their ears for any sound. But nothing unusual could be seen or heard.

At a whisper from Derry they moved on and set to row around the island. The water was deep right up to the foot of the cliffs, but rowing was no easy matter owing to the sluice of the racing tide.

They went in on the north side of the island and made a slow circle of the whole rock. Nowhere could they find the ghost of a foothold. The channel on the south side was the narrower. It was not more than a couple of hundred yards in width, and the cliffs on both sides overhung so much that only a mere rift of sky was visible overhead.

It was here that the silent boatman had disappeared, and it was here that Derry made his closest search. It was useless. So far as they could see in the dim starlight there was not room for even a seal to land.

"Pull out!" whispered Derry at last, and no one spoke until they were back behind the southern point.

"Done in the eye again, old son," said Ned, with a poor attempt at cheerfulness. "There's no landing place on that big black rock."

"No," said Derry. "It was on the island. I'm certain of it. They've probably got a derrick from a cave mouth up above, and hauled him up with that."

"They won't have a chance," said Derry grimly. "We'll do the hauling up if there's any necessary."

"Since we can't get up from below, we must get down from above," replied Derry quietly. "To-morrow morning we shall go straight back to Cromarty, and return to-morrow night in the Argonaut. Then we shall have something to say to Mr. James Spain."

CHAPTER XXVIII. — THE GUARDIAN OF THE ISLAND

DERRY HOLT and his cousin, Ned Barlow, are on the track of a pirate airship. They make for its lair in their own dirigible, The Argonaut.

"So that's your scheme, Derry?" said Ned. "But how can you tell that you'll hit off the island?"

As a matter of fact there was no need to try again. So accurately had Derry calculated the force and direction of the breeze, that soon it was plain that the airship would drift across the very centre of the island.

Derry and Ned already had their parachute belts around them, prepared for their expedition. They carried pistols, electric torches, candles and matches, a first-aid outfit, and a flask of brandy. Also each had a good sturdy stick.

Green, their trusted engineer, was to be left in charge of the ship. He was very much upset about the whole performance, and wanted badly to go with them; but Derry would not hear of it.

"Two's plenty for a job of this sort," he explained. "We are only scouting, remember. Now, see here, Green, you are to let her drift a bit inland, then anchor. If we want you we fire our red lights. Then you can come as sharp as you like."

Three acres don't give much room for a landing by parachute, and both knew the risk of missing the summit altogether. Hulme, however, was below with the boat to pick them up, if necessary.

Luck was with them, and both landed safely on the close- cropped turf on the top of the crag. Derry was unbuckling the belt of his parachute when Ned joined him.

"If there is a hole, it's going to be a job to find it," he remarked. "That is, unless we can use our torches."

"Don't be an ass," was all that Derry said, and started off quartering across the short turf.

It was very gloomy, and next minute Derry nearly fell over some dark object which at once sprang up.

Derry turned aside. But the bull, annoyed at being roused like this, suddenly lowered his head and made a rush at him. So quick was the animal that Derry only just managed to spring aside.

Small as the bull was, the creature had a terrible pair of horns, and he was almost as quick and active as a goat. He spun round, and came at Derry again.

In trying to avoid the bull's second charge, Derry caught his toe on a projecting rock, and came down heavily. But for Ned the brute would have gored him.

Ned saw what was happening, and came rushing up with stick upraised. Just as the bull lowered his head to gore Derry, Ned brought his club down across the nape of the animal's neck with a force that splintered the stick, but brought the bull to his knees.

Ned seized Derry by the arm, jerked him to his feet, and the two started running just as the bull staggered up and charged once more.

Run they both did; but the worst of it was that there was nowhere to run to. The top of the islet was as bare and open as the palm of a man's hand. Before the two knew where they were they found themselves penned between the bull and the edge of what seemed to be sheer cliff.

The bull, half-dazed by the shock of Ned's tremendous blow, was not coming so fast as before, yet there was no doubt whatever about the ugliness of his intentions. To make matters even worse a second animal was in sight, coming up from the far side.

"No, not if we can avoid it. It would give the whole show away. There's a ledge here, Ned. If we get on to it the brute can't reach us."

As he spoke, he swung himself over, and Ned had just time to follow his example before their enemy arrived on the cliff top, where he stood tossing his fierce head.

"Glad you think so," grumbled Ned. "Seems to me like a cross between a tight rope and the edge of a razor."

For a fact, it was a ticklish place. There was just foothold and no more, and far below in the darkness they heard the swift tide fretting under the foot of the tall cliff.

"It's better here," said Derry, and sure enough the ledge, which sloped downwards steeply, grew wider below.

"But what's the good of this?" demanded Ned. "We shan't get any forrader, hanging on here like flies on a window-pane."

Derry did not answer. He had vanished around a bulge of rock. Next moment his head popped back into sight.

"Ned," he said eagerly, "Ned, there's a hole in the cliff face. A cave mouth, I'll be bound."

Sure enough, there was a small opening in the face of the cliff, so small that Ned had a job to wedge his big shoulders through. But he managed to squeeze in and found the passage wider as he got farther inside.

Derry flashed his torch. It showed a sort of rock burrow sloping steeply into unknown depths.

It was wicked going, and after ten long minutes of creeping and crawling and knocking bits off himself Ned got very fed up.

"The end of it will be that we shall stick down here and never be able to get back at all," he grumbled.

Derry was not listening. He was kneeling, with his head up, sniffing like a pointer on the scent of game.

CHAPTER XXIX. — IN THE HEART OF THE ISLAND

DERRY went on at top speed, yet with wonderful silence, while Ned followed close behind. The petrol smell grew stronger and stronger, and presently the pair found the passage widening. Then, without warning, they were in a great low-roofed cavern, and all around were stacked drums and drums of petrol— thousands of gallons in all.

"We've got it," he said in a voice that trembled with excitement. "It's the real thing at last, Ned."

Before Derry could answer there burst out from the distance the chorus of Stevenson's famous pirate song:

The song echoed in the weirdest way under the rock roof of the cavern, and Derry turned swiftly to Ned.

It was not quite dark in the petrol magazine. A little light leaked in from somewhere beyond, just enough for the boys to find their way among the petrol drums to an opening on the far side.

Stepping cautiously out of this, they found themselves in a cave of gigantic proportions, dimly lit by a single oil lamp dangling from the lofty roof.

Derry drew a quick breath and pointed. There, in the centre of the cavern, lay the great bulk of Spain's airship, the yellow cover glinting faintly in the dull light.

The sound came from under a low arch of rock opposite, where—in some farther cave—Spain's crazy crew were indulging in a musical evening.

Derry looked around. At that moment steps were heard clinking on the rock floor. Both boys drew back softly into the mouth of the petrol cave.

The steps rang nearer. Peering round the corner they could see a man coming down the cave from the inner end. There was not light enough to see his face, but he was short, thickset, and dressed in dark brown overalls.

"He's coming right past us," whispered Ned in Derry's ear, "Couldn't we—couldn't we collar him?"

The man came nearer. He was walking carelessly. He had not the faintest idea that two pairs of keen eyes watched his every movement.

Derry saw Ned tense himself. Then, as the man came opposite, Ned sprang. Big as Ned was, his leap was soundless as a cat's, and before the man had time even to turn his head, Ned's powerful hands clutched him round the throat.

Derry sprang forward to help, but before he could reach the spot, the man was on his back on the floor, and Ned kneeling on his chest.

"Make a sound and it's your last," Ned hissed at him with a ferocity of which Derry had never believed him capable.

The wretched man, half-choked, half-stunned, and completely paralysed by this surprise attack, merely lay on his back, gasping for breath.

"Sharp!" snapped Ned. "We've got the lot of you this time. The place is surrounded."

They let him up. Ned drew his pistol and held the muzzle tight against the man's body.

The man led the way up the main cave to an opening on the opposite side. The boys saw that there were several of these alcoves off the main cave. The opening was closed by a rough iron gate, bolted on the outside.

There was Mr. Murston lying sound asleep on a bed made of a couple of sacks stuffed with heather.

The light roused him. He opened his eyes. It was characteristic of the man that he did not call out or make any noise.

"Ay, boys, I thought you'd find me," he said. "But I hardly hoped you'd be so quick. How did you do it?"

"Tell you later," replied Derry quickly. "We've got to get out sharp now. This way."

There was a quick rush of feet. Ned gave a sharp exclamation and dashed for the opening.

For an instant he had taken his eye off his prisoner, and the man had seized the opportunity to bolt.

"This way. Quickly!" he said, and seizing Mr. Murston by the arm took him at a run across the main cave.

"Help!" they heard their late prisoner shouting. "Here, Spain, Musgrave, Coyle."

The singing changed to a roar of rage, and from the lighted opening to the left poured a stream of fierce-looking fellows, headed by the very man whom the boys had seen leaving the old mine mouth on the previous day. Derry caught a glimpse of that fierce, hawk-like face, and knew him for Spain himself.

A shot crashed out, waking bellowing echoes in the great hollow place. But the three fugitives dived like rabbits under the low arch of the petrol cave, and threading their way among the drums and cases raced for the tunnel mouth beyond.

"You first, sir," panted Derry, shoving Mr. Murston into the opening. "You next, Ned. You'll have to help him. I'll be all right. I've got my pistol. I can hold them off."

Ned did not wait to argue. He dragged Mr. Murston upwards. Spain and his men were stumbling among the cases. Derry had shut off his torch, and not one of them had a light.

Spain was shouting to someone to bring one, and next moment there was a red glare as a fellow rushed in carrying a smoking oil lamp.

By its light, Spain saw Derry at the entrance and fired again. The bullet flattened on the rock within a foot of Derry's head, and he fired back.

He had not aimed at anyone in particular. He merely wanted to show them that he was armed, and so keep them back. But his bullet, fired at random, hit the man carrying the lamp, or else perhaps the lamp itself. There was a yell, a crash of broken glass, and a bright flash of flame.

Yelling with terror, Spain's men bolted like rabbits, falling over one another in their frantic efforts to get away. Derry, too, saw the danger, and, turning, scuttled upwards after Ned and Mr. Murston.

"Hurry!" he cried. "Hurry! There's a lamp smashed among the petrol. The cave will be a furnace in two twos."

He was right. A few moments later there was a loud explosion below, and at once a gust of hot air came rushing up behind them. The two boys, alone, could have escaped easily, but in that narrow, steep tunnel stout Mr. Murston was at a dreadful disadvantage.

The heat grew frightful, and a thick, black smoke poured up, filling their throats and eyes.

The scramble became a nightmare, and had it not been that they had got a long start they would never have done it. As it was, they just managed to reach the top and staggered out on the ledge, more dead than alive.

But Derry still had his wits about him, and the very moment he was out, he sprang past the others, scrambled to the top, and put a match to his flares. A great red glow rose into the night, and a moment later an answer came from the air a mile or so away.

"There nothing left for her to do," Ned answered. "The cave must be a fiery furnace. Spain and his crowd must be grilled alive."

As he spoke the great air ship came dipping softly down out of the night, with a rope-ladder dragging across the turf.

"Leave me here. I shall be all right," said Mr. Murston. "You go and smash Spain."

Derry knew delay was dangerous. He obeyed, and he and Ned sprang swiftly aboard. Green didn't say much, but it was plain how delighted he was to see them safe.

Derry hastily explained, but before he could speak a dozen words there was a shout from the look-out that Spain's ship was in sight.

Up she came out of the narrow strut, rising like a bubble. But Derry was ready for her, and as she rose so did he. His guns were ready manned, and a storm of bullets burst upon Spain's doomed ship.

Spain fired back, but this time he was at a disadvantage. His men had scrambled aboard in a frantic hurry, and nothing was in fighting order.

Through the darkness the tracer bullets from the Argonaut cut long streaks of fire, and the Brock incendiary bullets followed them.

"Got him," snapped Green a moment later, and sure enough a thin wisp of scarlet flame was creeping along the upper surface of Spain's forward ballonette. The hydrogen which filled it was afire.

The Argonaut shot up into the sky. Only just in time, for next minute the night was shattered by a tremendous explosion. A glare of fire which was seen for fifty miles lit sky and sea, and wide spaces of lonely heather.

As it died down, the burning remains of the pirate craft fell hissing into the sea.

For some seconds Ned and Derry stood side by side looking down into the darkness.

On returning to Cromarty a report was at once dispatched to Lord Meripit, who wired back immediately:

THE END

THOMAS CHARLES BRIDGES (WRITING AS CHRISTOPHER BECK)