Whilst these events were in progress Captain Crouch and Jimmy Burke, in the great seaport town of Hull, were hot upon the scent of Rudolf Stork.

From the railway station they drove straight to the central police station, where they found the inspector in his office. Scotland Yard had telephoned during the night that Stork would probably arrive in Hull early in the morning. Detectives had been dispatched at once to the railway station, but got there too late to arrest the spy, who was probably the only first-class passenger who arrived by the one forty-seven train from King's Cross, who had no other baggage than a small handbag, and who was met by a motor-car in which he went off in the direction of the docks.

The police had made sundry inquiries among the fishing people in the poorer part of the town, and had learnt that the smack "Marigold" had put to sea in the small hours of the morning.

Crouch saw that there was nothing to be done but to continue the pursuit, even into the midst of the shoals and fog-wreaths of the Dogger Bank. He knew well the maxim that it was wise to set a thief to catch a thief, and decided to follow the "Marigold" in another fishing-smack, and not a steamer.

His reasons for this were twofold. In the first place, the Well-bank was extremely shallow water, across which no ocean-going ship could pass. Secondly, as he knew full well, in view of the forthcoming raid, the neighbouring waters were alive with enemy submarines, who were more likely to torpedo a steamer flying the English flag than a comparatively valueless fishing-boat.

Now, the name of Captain Crouch's friends was legion, but for the most part they lived, moved and had their being in seaport towns, and there were not a few in Hull.

One of these was a Grimsby man, with nearly thirty years' experience as a trawler, who was known as Captain Whisker; and it was to his house that Crouch and Jimmy Burke betook themselves, as soon as they had gleaned all available information from the police.

Though it was still exceedingly early in the morning Captain Whisker was up, digging furiously in his garden, with a blackened pipe between his lips. He was a man the very opposite of Crouch. Crouch was small and wizened; Whisker broad, florid and colossal. He could not have been less than six feet five in height, and his chest measurement was exceeded only by the girth of his waist. He was clean-shaven, but his eyebrows were so extremely large and bushy that they resembled a kind of superior moustache, and made his surname of "Whisker" seem singularly appropriate.

"Why, Crouch!" he exclaimed, driving his garden fork into the ground and coming forward with outstretched hand. "The last man on earth I ever thought to see! It must be five years, at least, since you and I were shipmates; and that was on the West Coast, when I took you down from Sierra Leone to Banana Point, when you were bound for the Aruwimi, to look for a lost explorer who, you said, was a good two inches taller than I."

"There's no time now to talk of that," said Crouch. "I've a job of work on hand, and you're the very man who can help. There's a German spy who put to sea at daybreak in the 'Marigold,' and I've a mind to go after him, if you know of a craft that can be safely recommended."

Captain Whisker drew himself up to his full height and puffed out both his cheeks, at the same time opening his blue eyes so widely that they resembled those of an enormous doll.

"Come inside," said he, almost in a whisper, after a pause sufficiently long to enable him to recover from his surprise. "Come inside, and talk matters out."

Crouch and Jimmy followed the burly captain into a very singular room, in which a hammock was suspended from the ceiling, whilst the floor was wholly taken up by fishing-nets, tarpaulins, ropes, boats' anchors, lifebuoys and a hundred odds and ends such as might be picked up on a sheltered beach near which a wreck had taken place. There was barely room in which to move.

Crouch told his story briefly--or as much of it as he deemed it was necessary for his seafaring friend to hear. When he had ended, Captain Whisker unburdened himself as follows--

"You can't do better," said he, "than set out in the 'Kitty McQuaire.' She's a faster smack than the 'Marigold'; she can do a good knot and a half better. I reckon she can sail nearer the wind than any sailing-ship of any kind between here and Aberdeen. She was going out this morning, in any case. I'll come with you, and take command. It's some years, Crouch, since you skippered a smack; and though I don't doubt that you still know as much of your old trade as I do, what you have told me has kind o' hoisted a flying jib before the mainsail of my curiosity; and I should like to see the business through."

"Come on, then!" Crouch almost shouted. "It won't be the first time, by a long chalk, that you and I were shipmates in adventure. And, what's more, you always brought me luck."

Resolved to waste no further time, they set out together; and long before the sun had reached its meridian, they were passing out of the mouth of the Humber, where they set their course to the north, towards the Well-bank lightship.

The "Kitty McQuaire" proved herself to be all that Whisker had said. As the afternoon advanced the sea got up, until by evening a gale was blowing from the south-east. The smack danced and dived and pirouetted, sometimes being lifted high upon the crest of the waves, and at other times plunging, nose foremost, into the depths.

Captain Whisker soon proved himself no less capable a seaman than Captain Crouch. Indeed, had it not been for his great knowledge of the sea and admirable presence of mind, it is more than likely that the "Kitty McQuaire" would have been driven on to a shoal or foundered in open water. They were obliged to haul down their sails, and keeping the smack head-on to the storm, to put their trust in Providence that they would not be driven back upon the shore.

That night to Jimmy Burke was a night of purgatory and terrible suspense. In the first place, he was unconscionably seasick. What he had endured upon the "Harlech" was as nothing to the torments he suffered now. In a very short time he was reduced to such a state of utter wretchedness that, in his fevered imagination, death by drowning was preferable to life under these conditions. For all that, he was filled with a great fear that the smack would, in truth, go down. Sometimes, when a great wave broke immediately before them, the salt water washed the ship from bows to stern, so that they were obliged to cling to the masts or whatsoever they could lay hold upon, to prevent themselves from being swept away.

In addition to the wind that shrieked and howled through the rigging, a denseness lay upon the uneasy surface of the waters. It was so dark that they could not see twenty yards before them, and knew not in which direction they were being driven by the wind. For some hours they lived in horrible anticipation that they would suddenly find themselves stranded on a sandbank or some lonely part of the coast, where the ship would be battered to fragments by the waves.

With the first signs of daybreak the fog lifted and a great blood-red sun, like an enormous Chinese lantern, arose from out of the east, to flood the desolate scene with a kind of purple-tinted twilight, such as one might suppose should infest a land of ghosts. At the same time, the wind dropped and changed further towards the south. Within two hours the sea had so abated that they were able to hoist their sails and to continue on their course.

Presently they caught sight of the coast, and Whisker recognized at once the white cliffs of Flamborough Head. They were much further north than they had dared to hope; if the wind continued to be favourable, they would reach the neighbourhood of the Well-bank soon after dark. Jimmy, also, had by midday sufficiently recovered of his seasickness to eat a ship's biscuit so hard that he was obliged to break it with an axe.

Early in the afternoon, since there were several ships in the neighbourhood--fishing-smacks, Government trawlers and steamers from the northern ports--they lowered a net to make a pretence of fishing and to avoid arousing suspicion. It is as well they did so, for soon afterwards they sighted a smack, a mile or so ahead, bearing on the same course as themselves, which Whisker recognized at once as the "Marigold," upon which--it was presumed--was Rudolf Stork.

The wind could not have been more favourable for their purpose. They were able to hold a straight course, and under full sail to bear right down upon their quarry.

It was not long before the "Marigold" appeared to guess that she was being followed, for her skipper hoisted all the sail the smack could carry, and changed his course a little to the north. By that time the "Kitty McQuaire" was about two miles in rear. The other ships had been left far to the south, with the exception of a large tramp steamer, with a funnel so aft as to appear to proceed from the poop, which was steadily ploughing her way northward, bound possibly for Leith or Inverness.

Though the "Marigold" strained every stitch of sail to widen the distance between herself and her pursuer, it was very soon apparent that she had little chance of escaping. The "Kitty McQuaire" was overtaking her quarry, inch by inch, gaining a yard or so with every gust of wind.

Captain Crouch from the bows of the smack regarded the "Marigold" through a long telescope that belonged to Captain Whisker, and upon which was emblazoned in blood-red letters the name of every ship upon which he had ever sailed. Crouch had already examined the tramp steamer to learn that she was the "Mondavia"--by a strange chance one of the fleet of Jason, Stileman and May, the very house to which Crouch himself belonged.

Suddenly, with a loud cry of triumph, he thrust the telescope into the hands of Jimmy Burke.

"Look there!" he cried. "There's Rudolf Stork, or else I never yet set eyes upon the man! He's got his eyes glued on us through a pair of glasses! There are not more than five men on board, so far as I can see; and there's a strange sort of arrangement aft, which might be anything from a cucumber-frame to a coffin! If we can overtake her before it's dark we'll have the whole gang at the Old Bailey under a week!"

He was wildly excited, as, indeed, he had some cause to be. By all the laws of chance Stork was as good as captured. It was plain the "Marigold" could not escape, for it still wanted two hours to sunset, and she was making no better headway. It appeared that certain success was well within their grasp. And it was just at this junction that there happened an incident which was at once disastrous and unexpected. The "Marigold" opened fire!

To be fired upon without warning on the high seas by an ordinary fishing-smack is not an event that one might look for; and neither are effective counter-measures possible when one is both unarmed and unprepared. The first shot struck the water ten yards from the "Kitty's" bows, whereas the next whistled high overhead, to plunge into the sea a long way astern. It was apparent that the suspicious arrangement which Crouch had noticed on the deck of the "Marigold" was one of those old-fashioned high-angle muzzle-loading guns which go by the name of mortars. As far as Jimmy Burke could make out with the aid of the telescope, the mortar was covered over with fishing-nets and tackle of all kinds, and Rudolf Stork was directing its fire.

Now the appearance of this new factor in the situation cast at once a very different hue upon the prospects of all concerned. In the first place, these weapons may be of no more use than pea-shooters when brought to bear upon a man-of-war; but one shot below the water-line of the "Kitty McQuaire" would suffice to send her to the bottom. Secondly, though Crouch, Jimmy and Whisker were all armed with revolvers, they had no weapon that was of the slightest value at a range beyond a hundred yards.

None the less, Crouch stoutly refused to give up the chase. He loudly protested that he would overtake the "Marigold" or go down to Davy Jones.

The "Mondavia" was then about four miles to the west, between the "Marigold" and the coast. They had no means of signalling to the steamer, since there was not a flag on board, and though there was a signalling lamp, this was quite useless whilst the daylight lasted.

At length, at the end of about ten minutes, the "Kitty McQuaire" was hit. One of the round projectiles from the mortar struck the mainsail obliquely, so that it tore a great rent that flapped open in the wind. Crouch clenched both fists, and stamped upon the deck.

"Are we to go ahead?" he cried to Jimmy. "Are we to go on with it, or give up the chase?"

"Go on!" cried the boy, who was quite beside himself with excitement. "I don't care what happens. It's too late to go back now."

They were then almost within revolver range of the "Marigold." Crouch went to the bows, and fired three shots in quick succession at the fugitives.

"Heave to, you curs!" he shouted at the full power of his lungs.

It was the voice of Stork that answered.

"Come and take us," he cried in loud derision.

"Do you think we dare not?" answered Jimmy.

Before Stork could answer, Crouch broke in again, telling Stork to blaze away with what he called his "pop-gun" which was not capable of knocking a hole through an empty rain-barrel. These words, in spite of the fact that they were never spoken seriously, were uttered at a most inopportune moment; for, hardly had they left the little captain's lips than a shot struck the starboard quarter of the "Kitty McQuaire" about a foot below the water-line.

Whisker was the first to recognize the danger, and ordered all on board to stand by the hand-pump, which was the only means they had of bailing the ship.

"And even that won't save us," he added in a doleful voice. "She'll fill for a certainty. She'll not take ten minutes to settle down."

The alarming truth of this was at once wholly apparent. Within the space of a few minutes, the "Kitty McQuaire" took on a decided list. At the same time, she slowed down; every second, the "Marigold" widened the distance between herself and her pursuer. As they lowered the sails, they heard Stork's loud, boisterous laugh, as the man looked back upon the sinking ship upon the deck of which his victims stood in silence, side by side.

Indeed, Crouch and his companions were face to face with inevitable destruction. Though the storm had subsided, the sea was still too rough to launch the only small boat the "Kitty" carried. This was a small dinghy used for harbour work, which could neither carry all who were on board nor live for two minutes in such a sea without being swamped.

The "Kitty McQuaire" was sinking slowly by the bows, turning over quite gently--like a tired beast that lies down to sleep. The deck was now so much aslant that they were obliged to hold fast to the masts and rigging, to prevent themselves slipping down, one after the other, into the cold, hungry sea.

The sun, at last, was setting. Darkness was spreading from the east; and at the same time, a lowering mass of cloud was drifting forward on the wind which presently would shut out the starlight and the moon.

There is no situation more terrible, there is nothing that requires greater fortitude to bear, than to find oneself doomed and deserted upon the unutterable loneliness of the sea, as the sun sinks in the sky and the mists of twilight glide upon the surface of the waters. There was no help for it; they knew that they must die. At such an hour, it was but human nature that their thoughts should turn to the God Who had given them life. Each man closed his eyes; and standing together, clinging to the last of the sinking ship, one and all prayed silently and swiftly that death might be easy, and that the wrong they had done in their lives should be forgiven.

And then, as if to make their lot more hard, the cruelty of their end more bitter, within a hundred feet of the fishing-smack, silhouetted against the red glow of a winter's sunset, there arose from out of the water, the shark-like, threatening form of the U93.