"Take the bridge, Mr. Hetherton!" he cried. "Lower a boat, men!"

The boat was lowered in a trice and Frank and a score of sailors sprang in. The launch darted toward Jack at full speed, Frank standing erect and with the quartermaster at the rudder.

They were close enough to see the struggle between Jack and the German commander in the water. Frank saw the man break loose from Jack and strike out for the submarine. He saw Jack make after him, and he saw something more.

Half a dozen German sailors leaped into the water and made for Jack, who apparently did not realize his own danger, so interested was he in the pursuit of the German commander.

"Faster!" cried Frank, and drew his revolver.

Now, for the first time, Jack realized his danger. But it was too late to draw back, and it is doubtful if he would have done so anyway.

"I'm going to get that fellow," he gritted between his teeth, referring to the German commander.

One of the German sailors struck at the lad with a knife. Jack caught the man's arm with his left hand and twisted sharply. There was a snap, and the knife dropped into the water. The sailor uttered a cry of pain and turning, struck out for the submarine with his good arm.

Two sailors now beset Jack on either side, and the German commander turned to renew the struggle.

"Kill him!" he cried angrily.

One of the sailors raised himself high in the water, and a knife flashed above him.

"Crack!"

A revolver spoke sharply and the knife dropped from limp fingers.

Frank, standing erect in the Essex's launch, had fired. Now, as has been said, Frank was a crack shot, and in spite of the pitching of the small boat, his aim had been true. The bullet had struck the German sailor's arm just below the elbow, shattering the nerve.

Perceiving the approach of reinforcements, at an order from their commander, the Germans turned and swam rapidly toward the submarine. The sailors reached the vessel and climbed aboard. Their commander did likewise.

Unmindful of the cries of his friends behind him, Jack also laid hold of the edge of the submarine and drew himself, dripping, aboard the vessel. A sailor near the conning tower raised his revolver in deliberate aim.

"Crack! Crack!"

Two revolvers spoke almost as one, the first Frank's, the second that of the sailor who aimed at Jack. But Frank's bullet went home, thus deflecting the aim of the man who covered Jack, and the German's bullet went wild.

The commander of the submarine, at this juncture, losing his temper at being pursued to the very door of safety, turned and sprang for Jack with a wild cry. He was a big and powerful man, and as he wrapped his arms about Jack, the lad staggered back.

But he recovered his balance in a moment and struck out with his right fist. Struck in the stomach, the German grunted and stepped back.

Now the remainder of the German crew came pouring on deck. At the same time Frank's launch grated alongside and his men poured a volley of rifle bullets into the enemy. The latter turned and scampered for safety below decks.

Jack, still struggling with the German commander, paused and looked around long enough to cry:

"After them, Frank! Don't let them shut you out."

Frank understood and led his men toward the conning tower at a run. Most of the enemy were already inside and descending, but Frank arrived in time to prevent the closing of the conning tower, which would have permitted the submarine to submerge, leaving the struggling figures in the water.

With the conning tower open, it was, of course, impossible for the U-Boat to submerge, for she would have been flooded immediately.

Frank's men made prisoners of the half a dozen Germans who had not time to get below, and then the lad ran over to help Jack.

"Keep away, Frank," said Jack. "I've got this fellow, and I hope he doesn't give up too easily. We've heavy accounts to settle with him."

The big German showed no symptoms of giving up. He lashed out with both arms and Jack was kept busy warding off the blows. But the German commander was a novice at this sort of fighting, while Jack, only a year or so before, had won the heavyweight boxing championship of the British navy. So there was no doubt in Frank's mind as to the outcome. He and his men formed a circle around the struggling figures, at the same time guarding the conning tower to prevent the enemy from closing it.

"Shoot the first head you see down there," Frank enjoined the men he left on guard, and he knew they would be only too glad to obey this order.

Jack, with a smile still on his face, permitted the German commander to waste his energy in ineffective blows. Then Jack stepped forward and delivered a heavy blow to the man's mouth. The German staggered back. Jack doubled him up with a left-handed punch to the pit of the stomach, then straightened him with a second hard right to the point of the chin.

The German commander reeled backward. Jack followed up his advantage, and for the space of a minute played a tattoo on the man's face with both fists. Then he stepped back, and as the German came toward him, the lad muttered:

"I guess this has gone far enough. Now for the finish."

He started a blow almost from the deck, and putting his full force behind it, struck.

"Crack!"

The blow could be heard even aboard the Ventura, which had approached close by this time.

The German commander seemed to stagger back all of ten paces, the British sailors scurrying back to keep out of his way. Then the man fell, his head striking the deck with a sickening thud.

"There," said Jack, "I guess that will settle you. Tie him up, men."

A wild cheer had burst from the sailors as Jack delivered the finishing touch. None of these men had ever seen Jack in action before, and it was only natural that they should be greatly impressed at this exhibition of their commander's prowess.

"By glory! What a blow!" one of them exclaimed. "Did you see it, Tom?"

"Did I?" exclaimed the man addressed as Tom; "did I? I'll say I did, and I thought I was pretty handy with my fists. But not against Captain Jack, not for me."

As bidden by Jack, the sailors rolled the German commander over and bound him. Then they carried him to the Essex's launch and threw him in, none too gently, either, for there was no man there who had not a disgust for Germans, German tactics and everything German.

"Now," said Frank to Jack, "I guess we may as well stand clear and let the Essex pour a few shells into the vessel, eh?"

Jack shook his head.

"No," he said, "we shall take possession of the vessel. Call down below and see if the Germans will surrender."

Frank approached the conning tower and called down.

"Hello!" he shouted.

There was no response.

"Hello below!" he shouted again in German.

"What do you want?" came a sullen voice from below.

"We're in possession of this vessel now," said Frank. "Come up here and surrender."