Above the inky surface of the North Sea, battalion after battalion of low-lying, black clouds rolled across the moonless sky, driven by a southerly wind that frequently lashed itself into gusts and squalls of short-lived violence. Like a shadow riding the white-capped rollers, the long, low form of the Knat plunged and reeled southwards in the teeth of the rising gale, her high bows throwing up cascades of ghostly white foam each time she met the full force of an on-coming wave. Upon the quivering bridge towering above the narrow, sea-washed decks stood Lawless wrapped in a hooded "lammy" suit, which had once been white but was now the colour of a coal-sack. In front of him a quartermaster, similarly attired, gripped the little steering-wheel and gazed alternately at the illuminated compass and the tiny light at the bows that showed which way the vessel was heading.

"Ease her a couple of points," said the Lieutenant, recovering his balance after a sudden lurch which had thrown him against the searchlight apparatus.

The quartermaster gave the wheel a twist, but his answering call was driven back in his teeth by a gust of rain which swept down upon the sea.

"'Ell!" he muttered, and again fixed his smarting eyes upon the tossing, swaying, illusive glimmer of light on the bows.

Lawless glanced over the man's shoulder at the compass-card and then started to walk—or rather stagger—up and down the bridge in order to exercise his cramped muscles. Each time he reached the end of the bridge he grasped the rail and tried to pierce the surrounding blackness for any sign of a vessel, friendly or otherwise, but without success, because it was impossible to see more than a few yards ahead even between the rain squalls. Presently he bent down, glanced at the illuminated dial of his wrist-watch, and swore softly. There was still another half hour before his junior officer was due to relieve him on the bridge.

But at last there came the sound of a bell, and before it had died away a muffled figure crawled up through a hatchway aft and proceeded to stumble and slither along the deck in the direction of the bridge. Its progress was slow and precarious, and the remarks which emerged from beneath the hood were such as will not be found in a dictionary of nautical terms. Eventually it reached the perpendicular iron ladder leading to the bridge and, mounting it, was assisted on to the platform by an unexpected lurch which landed it somewhere in the vicinity of the quartermaster's sea-boots.

"That you, Trent?" inquired the Lieutenant, gazing down upon the recumbent bundle of clothes within which was concealed the person of Sub-Lieutenant Trent.

The figure slowly scrambled into an upright position, but without ceasing to emit curses upon the universe in general and the weather in particular.

"When you've quite finished offering up praise for having been born a sailor bold I'll leave you in charge," said Lawless. "Keep a southerly course and look out for submarines."

"Submarines!" snorted the junior officer. "Why not aeroplanes as well? It'd be as easy to see one as the other a night like this."

"Well, keep a bright look-out."

"A bright look-out——" the Sub-Lieutenant's reply was drowned by another squall, and Lawless, with a sigh of relief, descended to the deck. Seeing the door of the galley open, he stepped in and demanded of the cook a mug of hot cocoa. With this between his hands the Lieutenant perched himself upon the locker and, in defiance of the rules of conduct towards subordinates as laid down by my Lords of the Admiralty, swapped weather anecdotes with the cook. Then, having finished his cocoa, he slid off the locker and started to scramble aft towards the hatch which gave entrance to his cabin. But he had not covered more than half the distance when out of the darkness came the sound of a shot.

The Lieutenant swung round, and as he did so the white beam of the Knat's searchlight suddenly flashed out and, after waving about like some gigantic feeler, finally came to rest at a point about fifty yards astern. Beneath its glare could be seen a small patrol steamer and alongside her with platform awash, a German submarine with U77 painted on her conning tower.

Forgetting all about his much-needed rest, Lawless hastened back to the bridge. From the fact that the submarine had not torpedoed the patrol boat, he concluded that the German commander had boarded her in the hope of obtaining some information from the skipper concerning the movements of the fleet. The conning tower hatch was open and a machine-gun on the for'ard platform was trained on the boat.

As he reached the bridge, the Lieutenant leant over the rail towards the gunner in charge of the quick-firer on the forecastle.

"Blot her out!" he yelled.

The long muzzle of the machine-gun swung round, tilted up and down once or twice, and then emitted a yellow flame followed by a deep boom.

"Damn!" ejaculated Lawless, and his comment was fervently echoed by the gunner. The shot, aimed a trifle too low, had struck the water some ten yards in front of the submarine, an inaccuracy pardonable enough considering how the destroyer was pitching.

Before the gunner could elevate his weapon and while the machine-gun on the "bandstand" aft was opening fire, three men were seen to scramble over the patrol boat's bulwarks and drop on to the platform of the submarine. But thinking, probably, that the loss of three men was better than the loss of the whole crew, the commander had closed the hatch and the submarine disappeared beneath the surface as the sailors alighted on her platform. Next moment they disappeared also, dragged down by the suction of the submerging vessel.

"To think we might have bagged that swine!" growled Lawless as he proceeded to leave the bridge once more. "Just my infernal rotten luck."

His comment was echoed in varied terms by the Sub-Lieutenant, the gunner and other members of the Knat's crew. It was, to say the very least, extremely annoying.

"Stand by with life-buoys!" shouted Lawless, as he reached the deck. He wanted to rescue the Germans if possible, partly from humanitarian motives and partly because he hoped to glean some information from them.

While Trent was bringing the destroyer round to the patrol boat, the gunner still stood behind his quick-firer, cursing his luck and calling upon all the gods to witness that he would have sunk "the blighter" (i.e., the submarine) with his next shot, and Lawless leant over the deck-rail trying to catch a glimpse of the men who had vainly endeavoured to regain the submarine before she sank. He was still trying to penetrate the gloom, when a shadowy figure was swept towards him and, leaning over the rail, he made a grab at it. In doing so he overbalanced and next moment found himself amidst the dark swirl of waters striking out with one hand while with the other he clutched the jacket of the man whose life he had attempted to save.

The German, he soon discovered, was not a strong swimmer, but with a vague idea that he was rightfully his prisoner and must not be allowed to escape, Lawless still retained his hold on the fellow's jacket. He soon found that his efforts to keep afloat and assist the other to do the same were taxing his strength to the utmost. Had he abandoned the German to his fate, the Lieutenant would have stood an infinitely better chance, but such a thought never entered his mind even when he began to realise that his strength was almost spent. The patrol boat and the destroyer had disappeared from view, and not even the searchlight was visible, from which Lawless deduced that he and his companion must have been carried astern in a very strong current, which still further minimised their chances of being picked up.

At last, when it appeared hopeless to struggle any longer and he had almost resigned himself to his fate, Lawless thought he heard a harsh, gutteral voice hailing him through the darkness. With his last remaining strength he struck out in the direction from which the voice had seemed to come, and a moment later he and his companion were dragged out of the water and over a curved, slippery surface.

"Gott im Himmel!" exclaimed someone, and Lawless, raising his head, found himself sprawling upon the platform of a large submarine—the same one, he felt sure, which he had recently attempted to sink. Then the man who had given vent to the ejaculation, asked him something in German.

"Don't understand your lingo," answered the Lieutenant, dragging himself into a sitting posture and observing that his questioner was a tall man clad in oilskins and sea-boots.

"Who are you?" demanded the other, this time in fairly good English.

"Lieutenant-Commander Lawless of the British destroyer Knat. Who are you?"

"Commander Carl von Ranheim of the German Navy," answered the man, and added, somewhat unnecessarily, "you are my prisoner."

Lawless, now somewhat recovered, gripped a handrail and dragged himself upon his feet. Two sailors, he observed, were assisting the man for whom he had risked his life through the conning tower hatch. Then, looking over his shoulder, he saw the distant beam of the Knat's searchlight still focussed upon the patrol boat; evidently no one had seen him fall overboard nor had he yet been missed.

"Well," he remarked turning to the Commander of the submarine, "what are you going to do with me?"

"I have a good mind to send you back where you came from," answered the German officer, jerking his head in the direction of the water.

"As a reward for saving one of your men, I suppose," replied Lawless. "Well, as you seem to be afraid of even one Englishman, perhaps it is the best thing you can do."

"Afraid!" repeated the other. "Ach! but suppose I take you down below you learn our secrets, eh?"

"We've captured so many of your boats that I don't think there are many secrets left for us to learn."

"Schweinehunden——" began the German angrily, but was interrupted by another man, presumably an officer also, who emerged from the hatch. The two remained in conversation for some moments, and then the Commander again addressed his prisoner.

"I shall put you where, for a time at least, you can do no harm," he said. "The rest will depend on yourself."

A moment later Lawless felt the throb of the submarine's oil-engines and the vessel, still awash, started to plunge forward. Soaked to the skin and shivering, for the water was cold despite the fact of its being a very warm night, he hoped that the commander would offer him something hot if nothing else, but the German appeared to have no such intention. He had mounted the platform on the conning tower, where, apparently, he was giving orders to the steersman. The fact that the English officer was clinging to the handrail on the for'ard deck and almost waist-deep in water, did not seem to trouble him in the least.

The vessel surged along through the darkness, and presently Lawless became aware of a familiar sound—the weird and melancholy clang of a bell-buoy. He now knew that the submarine was heading towards the coast, and was amazed at the German Commander's temerity in venturing so near when, at any moment, the searchlight of a passing warship or patrol boat might suddenly flash out upon him. And now the mournful clang of the bell-buoy grew louder, and a fanciful idea occurred to Lawless that it was tolling for the hundreds of men who had perished in the North Sea by mine and submarine. The U boat passed within twenty-five yards of it, then slowed down and came alongside a cage-buoy, round whose iron pillar one of the German sailors cast the bight of a rope.

"Now," said the Commander from his platform, "you can disembark."

"What?" inquired the Lieutenant, not quite grasping the situation.

"You must get on that buoy," answered the German. "If you're not washed off before morning you'll probably be rescued by one of your own ships."

Lawless, as he gazed at the plunging buoy, felt his heart sink. Tired out as he was, he strongly doubted his ability to cling on to the buoy for an hour, let alone a whole night.

"Look here," he said, "you'd much better have chucked me overboard and done with it."

"Oh no, we Germans don't murder our prisoners," replied the other sardonically. "If you get washed away, that's not my fault. As you English say, 'It's up to you.'"

"Hanged if I'll ever try to save the life of a German again," said Lawless bitterly.

"Come now, Herr Lieutenant, I can't stay here all night!" cried the Commander.

There was nothing for it but to obey, and so Lawless, with the aid of the rope, managed to reach the small, oscillating platform and grip the iron stanchion which supported the spherical cage. Then a man on the submarine gave the rope a jerk, it slipped off the buoy, and the U boat stole away in the darkness.

It did not take Lawless very long to realise the full gravity of his position. He calculated that at least six hours must elapse before it became light enough for him to see, or be seen by, passing ships, and by that time he would probably be dead. As for making signals in the darkness, that was impossible, for he had nothing to make them with—not even a revolver. There was, of course, a faint chance that the Knat might make a search for him and perhaps discover him before it was too late, but it was far more likely that, assuming he had been drowned, Trent would proceed southwards.

Still, although he felt almost hopeless, the Lieutenant clung with grim tenacity to the iron standard, but for which he would have been washed off the slippery platform in a few moments, while across the wild waste of black waters came the dismal knell of the bell-buoy. The sound did not cheer him—in fact, it struck him as being unpleasantly prophetic.

"I wish," he murmured, "I could silence that damned thing."

Then he had an inspiration. If he could manage to swim to the bell-buoy and muffle the clapper some of the patrol boats in the neighbourhood would be bound to notice its silence and proceed to investigate the cause. The sound of the bell was of such importance to navigation in these waters that it would be missed almost immediately.

"Blowed if I don't try it," thought Lawless.

The chances of rescue by such a device might not be very brilliant, but it seemed the only thing left for him to do unless he were content to remain passively on the cage-buoy till he had to release his hold through sheer exhaustion.

The bell-buoy, he knew, was about a hundred yards distant, and in the daylight with a calm sea the swim would have amounted to nothing at all. But now the conditions were very different; he could not see the buoy and would have to guide himself entirely by the sound of the bell—added to which, the sea was rough, and he was still feeling exhausted from his recent struggle in the water. But, having decided that this was his sole remaining chance, Lawless did not hesitate and, first divesting himself of his heavy "lammys," slid into the water. The current dragged him right under the buoy, but after a struggle he managed to swim clear of it, and then struck out in the direction whence came the sound of the bell. At first he had little difficulty in making headway despite the choppy sea, but presently his stroke grew weaker, the muscles of his shoulders seemed as if they were on the point of cracking, and he found himself swallowing mouthfuls of salt water. A feeling akin to panic seized him, and he began to "dog-paddle" furiously, conscious only of a frantic desire to keep his head above the inky waves which descended upon him in an unending succession. For a moment or two he experienced all the horrors of approaching death by suffocation, and then, with a gigantic effort of will, threw off the numbing horror and struck out again with slow but steady strokes.

At last he caught sight of a dim, towering mass from whence came a harsh clang. He swam round it, and was lucky enough to encounter a large iron ring in the base, with the assistance of which he succeeded in dragging himself upon the narrow platform of the buoy. Here he remained for some moments lying on his chest, too exhausted to move. After a while, however, he recovered somewhat, though almost deafened by the clangour of the huge bell above his head. Tearing the woollen comforter from round his neck he climbed up to the bell and managed to wrap it round the clapper, thus effectually muffling it. This done, he slid down again and prepared to await whatever might happen.

It seemed to him that he had sat there for hours interminable, drenched by the waves and in peril of being washed off every moment, when he became aware of something grinding against his boots. He could not see what it was, but bending down felt with one hand and discovered a chain, which appeared to be attached to one of the ring-bolts round the base of the buoy.

"Now what the dickens is this for?" he asked himself.

A buoy, as he knew, is moored by chains attached to the bottom and not to the side, which would cause it to float askew. Besides, the chain grating against his boots was much too light to hold in position a mass weighing several tons and in weather such as this would have snapped like a thread. Therefore it was certainly not a mooring chain.

At the risk of slipping off the platform, Lawless twisted his legs round the pillar supporting the bell and, leaning forward, caught hold of the chain and tugged at it with both hands. It came in quite easily at first, and then stopped with an abruptness that nearly jerked the Lieutenant into the sea. He could see nothing, but passing one hand down the chain he felt something at the end—something large and buoyant, with sharp square edges like a box or a tank. Also he knew by the feel that it was metal.

Lawless forgot his own sufferings in contemplation of this puzzling discovery. What on earth, he asked himself, was the object of having a floating or submerged tank attached to this buoy? What did it contain? He pondered the matter for some minutes, and then, for the second time that night, had an inspiration.

It must be a secret petrol tank for the use of German submarines!

In a flash he divined the whole scheme. The bell-buoy, being such a well-known navigating mark, could not be mistaken for any other buoy in its vicinity. It was close to the English coast, and the tank attached to it could be replenished either by submarine petrol boats or by secret agents ashore—probably the former. On a dark night, such as this for instance, an enemy submarine could easily take on a fresh supply of petrol from the tank, while the latter, being submerged several feet below the surface, would not be seen in daylight. Doubtless, also, it was provided with an automatic arrangement whereby, when emptied of petrol, it became filled with sea-water, thus preventing it from floating on the surface and becoming visible. It was a most ingenious device, quite simple and, no doubt, an inestimable boon to belated enemy submarines which were running out of petrol. But the point was, having discovered this, how could he make use of it to the best advantage?

Lawless was so engrossed by this problem that he forgot to wonder whether his scheme of muffling the bell would lead to his rescue until the sound of engines in the darkness aroused him from his contemplations. Then, realising that a boat of some sort was at hand, he shouted as loud as he could. There came an answering hail out of the darkness, and next moment the Lieutenant was momentarily blinded by the dazzling rays of a searchlight turned full upon him.

"Ship ahoy!" he shouted.

"Hullo there!" came the answer. "What the devil are you doing?"

He recognised the voice of Sub-Lieutenant Trent and knew that it was the Knat's searchlight which was dazzling him. Then, as the destroyer drew nearer, Trent, in his turn, recognised the soaked and huddled-up figure clinging to the platform of the buoy as that of his senior officer.

"Stand by to jump aboard!" he yelled.

With considerable skill he brought the destroyer round the buoy so close that her side grated against it, and Lawless, clutching at the deck-rail, swung himself on board.

"Trent," he said, catching his astonished junior by the arm, "come with me into the chart-room, but first of all tell the steward to send me up a cup of hot coffee and rum."

When they were in the chart-room together, and Lawless was imbibing the stimulating beverage, he related between gulps his amazing adventures since falling overboard, as well as a plan for trapping submarines.

"I'm almost convinced," he concluded with cheery optimism, "that everything happens for the best after all."

"But supposing your tank theory is right," said Trent, who secretly doubted the accuracy of the Lieutenant's deductions, "how d'you know any U boat will tap your tank to-night? Seems to me the best thing would be to wait till morning and then sink the thing."

"And lose the chance of doing in at least one enemy submarine!"

"Or we could tie up to the buoy and plug any U boat that came up to the surface."

"Why, you fathead!" exclaimed Lawless, "if we tied up to the buoy the bally submarine might come up immediately under our keel. And if she didn't, how are we to spot her on a pitch-black night like this? You might turn on the bull's eye, but they'd spot the light through their periscope and either torpedo us or do a bunk. No, you must stick to my plan."

"H'm, perhaps you're right."

"And there'd be no sport your way."

"As to sport——" began Trent, but the Lieutenant cut him short.

"You'll carry out my instructions," he said, curtly. "Now bear down on that buoy again."

The destroyer approached the bell-buoy once more, and Lawless, having provided himself with a loaded revolver, prepared to resume his former uncomfortable post on the tiny, wave-washed platform.

"Remember," he said, when about to spring on to the buoy, "you've got to start operations before the sound of my shot dies away, otherwise we draw a blank."

He swung himself over the deck-rail, reached the buoy safely, and next moment the searchlight was switched off and the Knat disappeared in the darkness. The first thing Lawless did was to remove his muffler from the bell-clapper so that the sound should serve as a guide to any enemy submarines that might be searching for the secret supply tank. This done, he settled down to wait, with what patience he could muster, for the arrival of his hoped-for victims.

For over an hour he remained there, half-drowned, cold and nearly deafened by the bell. Presently he began to wonder whether, after all, he might not have made a mistake in his deductions concerning the tank. It also occurred to him that if this proved to be the case and he captured nothing but a severe attack of rheumatism, he would become the laughing-stock of the Fleet. He could imagine how the story would be passed from ship to ship with suitable elaborations. "Heard about that silly ass, Lawless? Spent the whole night lashed to a bell-buoy, fishing for German submarines with a bent pin and a petrol tank for bait!"

He was still considering what steps he could take to prevent the tale of his adventures being spread abroad, when something very black and solid arose out of the water only a few yards away. Although, considering the darkness, it was quite unnecessary, he crawled round to the other side of the buoy in order to take advantage of the "cover" afforded by the pillar supporting the bell, for he knew that black object must be the conning tower of a submarine rising to the surface. Then he heard voices, and at the same moment the chain attached to the tank began to slide over his boots, showing that the Germans were hauling it alongside their vessel. The moment for action had come.

Drawing his revolver he fired it in the air, and before the report had died away the buoy and the submarine were lit up by the brilliant beam of the Knat's searchlight. The Germans, of whom there were several on the U boat's platform, made a simultaneous rush for the open hatch, for all the world like startled rabbits diving into their burrows. But before they disappeared inside a yellow flame flashed out from the vicinity of the searchlight, followed by a dull roar. Another and another followed in quick succession; the submarine suddenly tilted up, gave a lurch, and then disappeared for ever beneath the waters of the North Sea.

"Pity you plugged that petrol tank as well," remarked Lawless as he and Trent sat at breakfast in the Knat's cabin. "We might have used it for bait quite a number of times."

"Couldn't be helped under the circumstances. However, I suppose this'll mean promotion for you and paragraphs in the papers headed 'Naval Officer's Amazing Ruse. How a German submarine was sunk.'"

"There's my official report," said the Lieutenant, handing the other a paper.

Trent glanced through it and looked up with a puzzled expression.

"You don't mention the bell-buoy," he said.

"Trent, do you consider that, in a stand-up scrap, I could lick you?"

The Sub-Lieutenant regarded Lawless in amazement.

"Why," he answered at last, "I suppose you could. You're nearly double my weight, and you've got a longer reach."

"Because," went on Lawless, "if you ever breathe a word about the way in which I collared that submarine I'll pound you so that your most devoted aunt won't recognise her dear sailor nephew."

He rose from the table.

"Sitting on a bell-buoy catching submarines with a bent pin! Why, it'd haunt me to my dying day," he murmured as he left the cabin.