Sorry about this, sir,' he said.

'So am I,' returned Biggles. 'How are you feeling ?'

'Pretty fair, sir.'

Able to walk ?'

I'll have a shot at it, sir.'

'Good. Then let's get up to the top.'

Briny looked surprised. 'To the top, sir ?' 'That 's what I said. It's no use going down because the place is full of Germans.'

Briny took a pace backward, his face a picture of consternation. 'Blimey he whispered.

Ginger led the way up the cave until they reached the b.u.t.tress of rock that dammed the water in the lake. They helped each other up, and from the top Biggles surveyed the water with a curious expression on his face.

'What do you think of it ?' inquired Ginger.

I think it's going to be very useful,' replied Biggles enigmatically. 'You're wet through already so you might as well come across with me. Briny, you stay here with Roy and keep guard. I'll leave this gun with you. If you hear anyone coming up the cave, let drive.

We shall hear you shoot and come back to help you.'

Biggles took off his clothes, and holding up the bundle with one hand, followed Ginger across to the ledge, where they discovered that it had stopped snowing, although the sky still looked very threatening. A hail brought Algy to the edge of the cliff above them. He lowered the line, and in a few minutes they were reunited at the top, where Biggles told Algy what had happened at the depot. 'How 's your machine ?' he concluded.

'We haven't tested it yet, but it should be all right,' answered Algy. 'The Flight-Sergeant found a piece of solder in the petrol lead; he's taken it out, so if anyone feels like taking off he can have a shot at it.'

Biggles contemplated the prospect without speaking, for it was enough to daunt the stoutest pilot. The maximum run over the smooth part of the rock was not more than a hundred yards; and that was not the worst. At the end of it, fluted columns of weather-worn rock rose vertically some ten or twelve feet in the air, which meant that a machine taking off, failing to get that amount of height, would collide with an obstruction that would smash it to pieces.

It might just be done,' decided Biggles at last.

Algy nodded. 'That's how I figured it. Who's going ?'

'You are.'

'Why me ? Why should I get away ?'

I'm not thinking about you particularly; I'm thinking about the German code-book. Von Stal-hein doesn't know we've got it, and it's worth its weight in gold to the Admiralty.

Whatever happens here that code is going home if it is possible to get it there.'

I doubt if I've enough juice in the tank to get to England,' said Algy dubiously.

Is there enough to get you, flying solo, as far as the North Sea ?'

'Yes, I should think so.'

'Then that's the way it will have to be. If, when you get to the North Sea, you can't spot one of our ships-well, I'm afraid it's going to be just too bad. But there ought to be plenty of shipping about-destroyers, mine-sweepers, submarine chasers, to say nothing of merchant convoys.'

'Why don't you go yourself ?'

'Because I've got something else to do here. You've got your orders-don't argue.'

As you say. What are you going to do ?'

'First of all I'm going up to the top of that lump of rock and have a look at the cove.' He pointed to the ma.s.sif up which Ginger had climbed. 'By the way,' he continued, 'you took a machine-gun with you last night. Is it still in your machine ? If it is I'll take it. With luck I might get a pop at von Stalhein, if he happens to be standing outside the cave.'

'Yes, it's still in my seat.'

Biggles walked up to the machine, and was lifting the gun out when he gave a cry of triumph. 'By jingo! I'd forgotten that!'

'Forgotten what ?'

From the rear seat Biggles lifted the time-bomb, which Algy had not used. 'This squib is the answer to a question I've been asking myself for the last half-hour,' he announced enthusiastically.

Algy stared. 'What's the big idea ? I'm not clever at riddles.'

'Does your imagination go far enough to give you a picture of what will happen when I blow this charge against the rock that holds all that water in the cave ?'

Algy's jaw dropped. 'You're crazy,' he declared. It would blow the cave to pieces. In fact, it might blow half the island to pieces. The tunnel would probably cave in and you'd be stuck up here with no way of ever getting down.'

Biggles laughed shortly. 'That 's a detail. What is more to the point, a million gallons of water let loose would sweep every man in the depot into the sea-and everything else.'

'But you don't know which way the explosion would expend itself,' put in Ginger aghast.

'You'd bust the dam all right, but you might blow the top clean off the island-or blow the side out of it, causing the whole place to collapse.'

'My orders are to destroy the depot if we have to abandon it,' answered Biggles grimly. '

Whatever else happened, the explosion would release the water, so von Stalhein and his gang would get their ears wet when they weren't expecting it-not that I care two hoots about them. I'm only concerned with flooding the depot before they can shift the stuff out of it.'

'This ought to be worth watching,' murmured Ginger.

Biggles's manner became brisk. Algy, put the code-books in the machine. I'm going up to the top of the rock. If anything unforeseen happens before I get back, take off and head for England. If you have to come down in enemy waters tie something round the British code-book and sink it. Ginger, you come with me.'

Putting the machine-gun on his shoulder, Biggles set off up the ma.s.sif.

It was not an easy climb when Ginger had attempted it, but now, with snow about, it was even more difficult. However, by strenuous labour, and by helping each other over the worst places, twenty minutes saw them at the top.

Ginger was the first to reach the edge and look down. He gave an exclamation of dismay.

Biggles joined him. 'That's von Stalhein's drifter down there, in the cove,' he said. 'I knew it was there. That looks like von Stalhein himself standing on the bridge, talking to the captain. I think I'll let him know that we're still alive.' He lay down in the snow, and taking careful aim, poured a stream of bullets down on the drifter.

Von Stalhein made a leap for the companionway and disappeared; some other men who were standing about also darted for cover.

'Rotten shooting,' said Biggles disgustedly. 'I couldn't hold the gun still in this snow; it jumped all over the place as soon as I pressed the trigger.'

A bullet splashed against a rock just below him, and whistled away into the leaden sky.

Biggles drew back. 'There's no sense in making targets of ourselves,' he said. 'They won't show themselves again for a bit. I've seen all I wanted to know, anyway, so we may as well get back.'

Ginger caught his arm and pointed seaward. 'What's this coming ?' he cried.

Biggles looked up. 'A couple of German destroyers, I fancy,' he said evenly. Ton Stalhein must have called them up by wireless. It doesn't make much difference; I don't see how we could have got out, anyway. We couldn't get near that flying-boat without coming under fire of the drifter. Let's hope the destroyers come into the cove.'

'Why?'

'You'll see. I think you'd better stay here while I go down and get the bomb in position. I'

ll ask Algy to wait until it goes off; then, if he gets back safely, he can tell Raymond what happened. You watch the destroyers. If they come into the cove, let me know by raising your arms above your head. I shall take that as the signal to blow the charge. Is that clear ?'

'Clear as daylight.'

'Good. I'll get down now. After the bang you'll be able to watch what happens.' Biggles smiled and hurried down to where Algy was waiting by the machine. His manner was still inconsequential, but his heart was heavy, for he knew that the last hour of the base had come, and he felt that he ought to have made better use of it. He knew, too, that except for something like a miracle, their own time had come. Whether they were blown up by the bomb, or whether they went down through the cave to surrender themselves to von Stalhein, it would come to the same thing in the end. Not that he contemplated going down. His orders were to destroy the base and he was thankful that he had a means at hand to achieve that object.

He had always had a feeling that the end might come this way, for it was as obvious to him, as it had been to Colonel Raymond, that such a base, situated as it was practically in enemy country, could not last for any great length of time.

'What 's happening in the cove ?' asked Algy as Biggles joined him.

It seems to be getting busy. There's a drifter and a German flying-boat already there, and two German destroyers just coming in,' smiled Biggles. Our friend von Stalhein might almost be justified in thinking that he has got us all safely bottled up at last.'

'Have you any reason to suppose that he hasn't ?'

'None whatever. Well, that's all. I want you to stand fast and wait for the result of the explosion before you take off. You will then be able-I hope -to tell Raymond that we wrecked the base before the Boche could shift the stuff. You'd better not start your engine yet. Von Stalhein has no idea that we've got a machine up here, and we don't want him to know, or the destroyers might start slinging sh.e.l.ls across before you can get off.'

Algy's face was expressionless as he held out his hand. 'Cheerio,' he said. 'I shall fly back here, of course, if I get the code-books home. If I can persuade the Air Ministry to let me have one I'll borrow a flying-boat; so hang on, if you can, on the off-chance.'

Biggles smiled as he squeezed Algy's hand. 'Do your best, old lad,' he said. Then, turning to the Flight-Sergeant: 'Bring the line and help me down to the ledge,' he ordered.

Whistling softly, he picked up the time-bomb and walked towards the cliff.

CHAPTER XVIII.

BIGGLES STRIKES BACK.

FLIGHT-SERGEANT SMYTH lowered Biggles to the ledge and waited for further instructions.

'Drop the rope,' Biggles told him. 'I shall need it. Thanks. Now listen carefully. You can see Mr. Hebblethwaite from where you are I think ?'

'Yes, sir.'

'Very well. There are two German destroyers on their way here. If they come into the cove Mr. Hebblethwaite will signal by raising both hands above his head. You will pa.s.s the information on to me via Briny, whom I shall send across to this ledge. I shall send Roy on over here too. I shall be at the far side of the lake.'

'Very good, sir.'

Biggles undressed, coiled the rope about his middle, and picking up the bomb, shouted to Briny to show a light. Arriving at the far side, he was pleased to find Roy looking much better, and sent him across to the ledge. He then ordered Briny to lower him to the bottom of the rock that dammed the water, where he waited until the message had been pa.s.sed on to him that Ginger had made the signal. He was relieved to get it, for more than once stealthy sounds coming from below suggested that the enemy were scouting up the fissure.

He timed the bomb for a quarter of an hour, and placing it in position, piled around it all the loose rock that he could find. He then ordered Briny to pull him up, and together they crossed over to the ledge, from where, after the rope had been thrown up, they were all hauled to the top.

Biggles ordered every one farther away from the cliff in case the explosion should start a landslide, and then looked about him. Ginger was still on the top of the ma.s.sif, looking down into the cove. Algy was standing by his machine ready to start up at an instant's notice. The others were standing near him.

'How long before the balloon goes up ?' shouted Algy.

I set the bomb for a quarter of an hour, so there are still about ten minutes to go. I'M going up to the top to join Ginger. Don't be in a hurry to take off. If anything unforeseen occurs get off right away without waiting for me to come down; otherwise hang on, and I'll try to give you some definite information to take to Raymond.'

Algy nodded. 'Good enough. But don't wait too long. I don't like the look of the weather; it may start snowing again.'

Biggles glanced at the sky. 'It doesn't look too good,' he admitted, and then set off up the ma.s.sif.

He was still only half-way up when there was a m.u.f.fled roar, and the whole island quivered like a jelly. He was nearly thrown off his feet, and for the next minute or two was kept busy dodging rocks that had been shaken loose and were rolling down the steep side of the ma.s.sif.

Ginger, lying at the edge of the cliff, watching the destroyers manoeuvre into position in the cove before dropping anchor, clutched at the rocks on either side of him as his perch shook under the violence of the explosion. Several pieces of rock on the face of the cliff were shaken loose and went hurtling down into the cove; some fell sheer; others struck the cliff again lower down and bounced far out over the water. Shouts of alarm rose from below; men appeared on the deck of the drifter, von Stalhein among them; others appeared at the mouth of the cave. Some were launching a dinghy.

After that there was a brief lull, although pieces of rock continued to detach themselves from the side of the cliff and whirl downwards, sometimes taking minor avalanches of loose shale with them. Then, from the very heart of the rock, it seemed, came a terrifying rumble, like distant thunder. The rock began to tremble anew, and Ginger experienced a feeling of acute alarm not far short of fear, for the sensation was one of lying on a volcano about to burst into eruption. His alarm was in no way lessened when a great ma.s.s of cliff broke away, and with a roar like an express train went plunging down into the void.

By this time the destroyers, their propellers threshing the water into foam, were turning towards the open sea. On their decks men were running about in a panic. The drifter followed; being smaller it moved faster, and trying to cut across the bows of one of the destroyers, came into collision with it. There was more shouting.

Ginger turned and saw Biggles coming hand over hand up the ma.s.sif. 'Look out!' he cried shrilly. 'The whole island's falling to pieces!'

The words had hardly left his lips when the cliff in one place started to bulge; it was as if it were made of elastic, and was being forced out under terrific pressure. Then, with a crash like thunder, the bulge burst. A mighty torrent of water shot clear into s.p.a.ce. Rocks and water went plunging down together. Simultaneously, from the mouth of the cave there issued a swirling yellow flood.

Ginger felt Biggles throw himself down beside him, but he neither looked at him nor spoke. He was too spellbound by what was happening below. At first the falling rock and water prevented a clear view, but as the first pent-up energy of the water subsided somewhat-although a cataract continued to pour down the cliff-the scene became clearer.

It was a terrifying spectacle that met his eyes, more like an upheaval of nature than an artificial catastrophe. Before the weight of water, the three vessels were being swept about like toy ships. One of the destroyers had rammed the drifter amidships and had stuck fast. Both were grinding against the spit that formed one arm of the cove. The second destroyer, with black smoke belching from its funnels, still had its nose pointing towards the cliff, but in spite, of its engines, was being slowly carried backward, and was in danger of colliding with the other two vessels. The flying-boat, being lighter, had already been swept out to sea, and now drifted helplessly.

The flood still pouring from the cave went swirling out to sea, a turgid yellow tide that carried with it all sorts of debris, and made a clear line of demarcation with the deep water. Men were clinging to the wreckage which, Ginger noticed, consisted largely of broken timbers, obviously the remains of the buildings of the depot.

'What a picture,' muttered Biggles in a tense whisper. 'I wish I had my camera. Raymond will never be able to say we didn't go out with a bang. What 's happened to the cliff underneath us ?' He strained forward trying to see it.

'Mind you don't go over!'

Biggles backed hastily. 'There seems to be a tidy hole there. I hope this piece we're on doesn't collapse; it doesn't look any too safe. Hullo, look at the drifter; she 's sinking. The crew are abandoning it judging by the way they're jumping on to the destroyer. There goes von Stalhein. That fellow seems to bear a charmed life.'

'He probably thinks that about you.'

Biggles grinned. 'True enough,' he agreed. 'The other destroyer's going to get away, now that things are a bit quieter.'

It looks like it. Still, she doesn't look any too happy. I bet her wireless is buzzing, asking for help. They'll have to hang around to pick up the people who are marooned on the rocks.'

Several marines, presumably survivors of the party that had been in the cave, had managed to secure a foothold on the rocks that ringed the cove.

'Well, what happens next ?' inquired Ginger, watching the second destroyer back slowly out to sea.