Biggles doubled round the last dune, and saw the soft gleam of the Didgeree-du's wings. '

Here she is,' he said quickly, and then, as the entire machine came into view, pulled up dead. 'Good heavens! That's done it,' he cried aghast.

Algy joined him. There was no need to ask what had happened: it was too painfully obvious. The incoming tide had flooded the creek to a depth that could be estimated roughly by the fact that gentle waves were lapping against the bottom of the fuselage.

The floats were under water, and the machine, for some reason not immediately apparent, had sunk over to one side. Water was still pouring into the creek, turning it into an ever-widening lake.

For perhaps a minute Algy could only stare at the scene as the enormity of the disaster slowly penetrated into his brain. 'I don't understand this,' he muttered. 'Why doesn't she float ?'

'Because her wheels have sunk into the sand, that's why,' answered Biggles grimly.

CHAPTER XIV.

VON STALHEIN AGAIN.

FOR the best part of an hour they strove desperately to drag the Didgeree-du from the sand that clung tenaciously to her wheels, but in vain, and Biggles reluctantly gave his opinion that they were wasting their time.

'She 's fixed as tight as a limpet on a rock,' he announced disgustedly. 'We shall have to wait for the tide to go down and then dig her out. It must be nearly high water now-I suppose that's why the flying-boat came here just at this time. We can't afford to lose the machine. I should look a pretty fool having to report to Raymond that we were down to a single aircraft.' Biggles sat down on the sloping side of a dune and regarded the du with disfavour.

'Waiting for low tide is all right as long as these chaps push off before daylight,'

remarked Algy. As a matter of fact I doubt if it will be right out before dawn. If the Boche take off in daylight they'll spot the machine for a certainty. D'you suppose they're going to fly calmly round and watch us dig it out? Not likely. They'd shoot us up--or send a radio signal saying that we were here.'

'You're becoming a perishing pessimist.'

It's no use blinking at facts.'

All right. Well, there's no sense in sitting here just staring at the blinking thing.'

'What do you suggest we do then-start a singsong or something ?'

'We might creep up to the shed and try to hear what the Boche are talking about. I mean, we might learn how long they propose to stay here. What are they up to, anyway ?'

'Refuelling, I expect-unless, of course, they've landed here to make mud-pies,' sneered Algy sarcastically.

'You talk as if you'd had a rush of mud to the brain,' declared Biggles with asperity, as he got up and began moving towards the shed, taking care to keep behind the dunes.

Algy followed him, and in a few minutes they were within sight of the building and the big flying-boat.

'They've put the cabin lights out,' observed Biggles. 'If that's anything to go by, they've no intention of moving before daybreak.'

It looks that way to me,' agreed Algy. 'Judging by the casual way that fellow is coiling up the hosepipe, they're going to stay here for the duration.'

They did not attempt to approach the door, for an occasional figure pa.s.sed in and out, but from where they were they could see that the big sliding doors had not been opened ; instead, a small door let into the larger one-an arrangement frequently used in such buildings-was being used. As there was nothing more to be seen from the position they now occupied they made a cautious advance to the hole in the rear of the building. Biggles had closed it when they had made their precipitate retreat, but it was only the work of a minute to lever it open again. They knew before they did so that some form of illumination had been turned on inside, for a shaft of yellow light poured through the open door, so they were not surprised to find that two large arc lamps, with shades to throw the light downwards, made the interior as bright as day. They could hear people moving about, and-a homely sound-the rattle of crockery; there was also a low buzz of conversation, but they could see no one on account of the high piles of stores that interrupted their view. What they could see, however, was the time-bomb, resting on the floor a few feet away.

I'm going in to retrieve that bomb ; we may need it,' whispered Biggles. 'I'll try to find out what they're up to at the same time. Stay where you are.'

There appeared to be no particular danger in fetching the bomb, for, by bending low, Biggles could keep under cover. Having reached it, he rose furtively and peeped over the top of a stack of sh.e.l.ls. The sight that met his eyes brought a smile to his lips, it was so human. Some distance away, perhaps a matter of thirty paces, some boards had been put across two piles of stores, forming a table. Round this were seated seven men, all young, still wearing their flying kit, but with jackets thrown open and helmets on the backs of their heads. They appeared to be in the best of spirits, as they had reason to be, for steaming plates on the table told their own story.

Not until then did Biggles realize how famished he was, and an insane desire to join the party came over him. He dismissed it reluctantly and tried to catch some words of the conversation, but as far as he could make out the men were not talking about their work at all, but-another human touch -were chuckling over a recital of the war rumours then circulating in Berlin.

Biggles remained where he was for some time, but then, as there was no indication that the conversation would turn to more relevant topics, he went back to Algy.

I can't hear much, but from their manner I should say they're going to stay here for some time,' he announced. 'At the moment they're having a lovely picnic.'

'Then what about shooting 'em up and having a basinful of soup ourselves ?' suggested Algy, ever practical.

It may sound silly, but that'd be a bit too much like murder for my liking. I've a better idea than that.'

'What is it ?'

I've got a feeling that I'd like to borrow their big boat.'

And abandon the Didgeree-du? Not likely.' 'We could come back and fetch it later on.' '

But they would find it.'

'Not necessarily. Anyway, if we covered it with mud and rushes there 's a chance they wouldn't tumble on it. They'll stick around the shed. My feeling is, if we can get hold of that boat we ought not to let the opportunity pa.s.s. The Didgeree-du may be bogged permanently for all we know, and if that turned out to be the case we should be in a fine old mess.'

'You're right there,' admitted Algy. 'All right then ; let 's have a dekko at the front of the building and see what 's happening there.'

'There 's no need for us both to go. You get back to the machine and start camouflaging it while I do the reconnoitring. I'll join you as soon as I can.'

Without protest Algy disappeared into the dunes. Biggles, taking the time-bomb with him, made his way to the front of the hangar, where he found his task even easier than he expected, for the place was deserted, and the great boat rode silently at her moorings, made fast by a single line from the bows. He scrutinized the shadows closely for a sentry, but he could not see one-not that he expected to, for had he been in the position of the chief pilot of the flying-boat he would not have thought it necessary to mount a guard.

Turning his attention to the door, a broad smile spread over his face as he realized how completely chance had played into his hands ; for the small door had not only been left open, but there, on the outside, was the key still in the lock. He waited for no more, but hurried back to Algy, whom he found just completing his task, made possible by the fact that the tide was now receding, and the creek was only inundated to a depth of two feet or so. It was now possible to see how hopelessly the Didgereedu was bogged, for her wheels, one lower than the other, were completely under the sand.

Biggles wasted no time in idle contemplation of it. 'Come on,' he said urgently. 'We're all set. The machine's as good as ours.' Briefly he related the circ.u.mstances. 'Lend me your pencil, and let me have a page out of your note-book,' he concluded.

'What 's the idea ?' inquired Algy as he pa.s.sed them over.

I'm going to slip a note under the door telling those fellows about the hole in the wall.'

'Why ?'

Otherwise they may never find it.'

'What does it matter ?'

'We can't leave the poor blighters to starve to death-anyway, they may be some time getting out, and I'm going to drop an egg on this place at the first opportunity. I should hate to do it thinking they might still be inside. Bombing's all right up to a point, but Algy nodded. 'Yes, to bomb the place after pinching their boat would be adding insult to injury,' he agreed. 'Well, let's get on with it.'

They returned to the store depot, where they found everything just as Biggles had last seen it. You get to the boat and make ready to cast off when you see me coming,' he ordered. 'The engines must still be warm, so they ought to start at the first spark.'

He gave Algy time to reach the boat, and a few minutes' grace after he had gone aboard, and then crept silently to the door. Very gently he closed it. The key turned in the lock without a sound. Then, taking the note he had written from his pocket, he slipped it through the crack. He could still hear the murmur of conversation inside ; it had gone on, unbroken, all the time he had been near the door, and he knew that the Germans were in blissful ignorance of what was happening. Picking up the time-bomb, more because they had only one or two at the base and he thought they might need it, than for any immediate purpose, he walked down to the flying-boat and went aboard.

It's all right, you can relax; there's no hurry,' he told Algy, who had cast off and was now sitting with his hand on the throttle.

'Shall I start up ?' asked Algy.

'Go ahead.'

Are you going to fly her or shall I ?'

'You,' returned Biggles briefly. 'I'm going to have a nap. Tell me when we're home.'

With his left hand on the master throttle, Algy started the engines, and the giant boat began to surge towards the open sea.

Biggles opened a side window and looked out, but nothing happened, for reasons which he knew. Still, he smiled at the thought of the consternation that must now be going on within the tin walls of the building.

The flying-boat rocked gently as she struck the swell of the Baltic; then her engines picked her up and she roared into the night sky.

Biggles noticed that Algy was laughing. 'Yes, war's a funny thing,' he remarked, supposing that he knew the cause of Algy's mirth.

It's funnier than you think,' declared Algy, going off into fresh peals of laughter.

Biggles looked at him curiously. 'Why this sudden flood of hilarity ?' he demanded. '

Come on, what's the joke ?'

'Did you ever read in the Bible about a camel going through the eye of a needle ?'

Biggles stared. 'I don't get it.'

I'm only wondering what we're going to do with this leviathan when we do get her home.'

Biggles frowned suddenly as understanding flashed upon him. 'Stiffen the crows,' he muttered, 'I hadn't thought of that.'

'Neither had I, until we started. She won't go into the cave, or anything like it. Even if we were able to pull her wings off, which I doubt, the fuselage would just about block the entrance.'

Biggles stroked his chin. 'It's just like you to think of something difficult when everything looked easy,' he observed bitterly. 'Work it out yourself. I'm tired. Tell me when we get to the island. I'm going to sleep.'

And sleep he did, until Algy nudged him in the ribs and warned him that they were nearly in.

Biggles woke up and stretched, yawning. 'That's better,' he announced as the flying-boat glided down to a smooth landing, with enough way on her to carry her to the mouth of the cave. Opening a side window he looked out, ready to hail if he saw anyone, for he realized that there was a chance of their being fired on. But the base seemed to be entirely deserted.

'Where the deuce is everybody ?' asked Algy.

I expect they're asleep,' returned Biggles. 'Don't make a noise , there's no need to wake them up,' he went on, as they walked along the huge, tapering wing of the flying-boat and jumped ash.o.r.e.

'Hm, this is odd,' he continued a few minutes later as they reached the depot, still without any one appearing. 'One would have thought there would have been somebody on duty.'

They went all round the depot, but the only person they could find was Roy, who, with earphones still clamped on his head, lay asprawl his desk, sleeping the sleep of exhaustion. The British and German code-books lay beside him ; the pencil with which he had been working was still between his fingers.

'Poor little beggar,' whispered Biggles, 'he's absolutely all in, which isn't surprising considering the length of time he's been at this desk. I suppose he tried to hang on until we got back, but flopped out over his work. You can't keep awake indefinitely. I've been asleep at the joystick before today. I think we may as well let him sleep on. Ginger isn't back, that's certain, but what on earth can have happened to Briny and the Flight-Sergeant.'

I suppose they've gone to look for Ginger.' 'Yes-of course, that's it. Well, I must say this looks a pretty dead sort of hole. Hullo! What's this ?' Biggles picked up a sheet of paper that lay by itself half concealed under Roy's face. Very gently he drew it clear and picked it up. It was marked across the top, in big block letters, URGENT. 'Good heavens, it's a signal,' he said tersely. 'It must have come in while we were away. Roy's decoded it, too-what's this ?'

Biggles read the message aloud. "Urgent. Enemy naval supply depot suspected on northeast coast of East Prussia, probably among sand-dunes north of the Gutte Channel. It is of vital importance that it be located immediately and destroyed."'

Biggles stared at Algy. 'What do you know about that ?' he muttered.

It must be the place we've just left.'

Of course it is. There couldn't be two of them so close to each other. What a confounded nuisance we didn't finish the job while we were there. Well, it'll have to wait now. I'm dead on my feet. I couldn't take a machine to that sandbank and back if the Empire depended on it. I can hardly see out of my eyes.'

'You look about played out,' murmured Algy seriously. 'You're certainly not fit to fly until you've had some sleep; you'd only crash and kill yourself if you tried. I tell you what; I'm fresher than you are ; you lie down and get some sleep. I'll take the Platypus and make a quick trip to the sandbank. I hope those fellows are not still inside the building.'

Biggles glanced towards the entrance of the cave and saw that it was now grey with the approach of dawn. 'They'll be outside by now,' he said definitely. 'They will have found my note telling them how to get out, so they'll probably be on the beach watching for a ship to take them off. When they see you coming they'll guess what you're going to do and clear of If they hang around it'll be their own funeral. After all, there 's a war on and orders are orders. All right, old lad. I'd be obliged if you would slip back and do the job; one bomb ought to be enough.'

I'll get along right away,' declared Algy. 'You get some sleep. When I come back we'll hunt round for the others.'

'Good! I'll see you off.'

Without waking Roy, they left the signals room and made their way along the catwalk to the Platypus. A single 1 12-1b. bomb was slung on the central bomb-rack, and Algy was about to get into his seat when Biggles picked up the time-bomb which he had brought back with him. 'You might as well take this,' he suggested. 'If you miss with your bomb, and the Boche are a fair distance away, you might land and do the job with this one. We'

ve got to make sure of the place. It won't take up any room, anyway, so no harm will be done if you have to bring it back.' He placed the square charge of explosive on the rear seat.

I tell you what would be a good thing to take,' said Algy suddenly.

'What ?'

One of those sub-machine-guns from store. If the Huns are still about, and I expect they will be, they might start shooting at me, and-well, I'd feel happier if I had a mobile weapon in case I had to land, or was forced down.'

'That 's true,' agreed Biggles. 'Stand fast. I'll fetch you one.'

He was soon back with a vicious-looking weapon, and some clips of ammunition, which he arranged securely within Algy's reach. 'Don't forget this is our last machine,' he reminded him as Algy climbed into the c.o.c.kpit.

I'll try not to bust it,' Algy promised.

Biggles ran to the mouth of the cave and looked up at the sky. 'Don't be too long away,'

he called. I don't like the look of the weather.'

Algy waved to signify that he had heard and taxied out on to the cove.

Biggles waited for him to take off and then made his way slowly to the mess. He looked into the kitchen as he pa.s.sed, wishing that he had the energy to get himself some breakfast ; but his one overwhelming desire was for sleep, and he lay back on his bed with a sigh of relief, not intending to sleep immediately, but to rest for a few minutes before undressing. But nature, long denied, decided otherwise. His eyes closed, and he sank into a heavy dreamless sleep of utter weariness.

The hour hand of the clock on the mantelpiece ticked its way slowly round the dial, and still he did not awake. Another hour went by and still he slept, unaware that the sun had been blotted out by a dark indigo curtain that rose swiftly from the northern horizon.

Presently, too, this curtain was blotted out by whirling flakes of snow that eddied about the entrance to the cave before dropping silently on the sullen water. And still he slept on, unaware of the silence, a sinister silence broken only by the relentless ticking of the clock on the mantelpiece.

He did not hear the tramp of feet that came cautiously along the catwalk. He neither heard nor saw the door open as Erich von Stalhein, an automatic in his hand, entered the room.