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."