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.