Perceiving that he could not out-swim his pursuer, the spy slackened his stroke, and just as Jack came up to him, dived. As he went down, he caught Jack by the legs and pulled him under also.
Taken at a disadvantage Jack struggled in vain to free himself. He was at a further disadvantage also, for the spy, before going under, had caught a long breath; whereas Jack had gone under sputtering and gasping.
But help came to Jack from a source he did not expect. When he had jumped into the sea in pursuit of the spy, Frank had done likewise, for he divined that Jack might have trouble recapturing the prisoner. While he was not such a powerful swimmer as Jack, he was nevertheless close at hand when the spy pulled his chum under.
Frank acted without an instant’s hesitation. Drawing his revolver and grasping it by the barrel, he also dived. Down and down he went, and then close beside him he became aware of the struggling figures.
The water was very dark, but the lad could dimly distinguish the form of his friend from that of the spy. Going close, he raised his revolver and brought it down on the spy’s head with all his force. At the same time he stretched forth his other hand, and seized the spy by the shoulder.
Freed of the hold on his legs, Jack immediately shot to the surface, where he filled his lungs with fresh invigorating air. A moment later Frank, still grasping the spy by the shoulder, appeared by his side.
“Lend a hand,” he called, “and we’ll get him back aboard.”
Jack, now greatly refreshed, did as his chum ordered and the two lads, supporting the body of the spy between them, swam back to the submarine, where willing hands helped them over the side.
Lord Hastings immediately took charge of the spy.
“Stretch him out there till he recovers consciousness, and then proceed with the execution,” he ordered.