As the physician forced some aromatic spirits of ammonia between his lips the lieutenant opened his eyes and gazed about vaguely. "What's the matter?" he asked weakly; but before anyone could answer he had relapsed again, and there was another wait of several minutes. But this time the lieutenant's mind was clearing. "Somebody shoved me--in that closet," he gasped, "and then--slammed and--locked--the door." He recognized the captain and the doctor. As his eyes closed again he added, in an almost inaudible whisper: "I was getting too close on somebody's trail." The captain looked at the ship's doctor significantly and dismissed the two oilers with instructions to return to their duties. "Found him locked in a small compartment down near the auxiliary engine room," the commander said briefly. "Hotter than blazes, and no air whatever where he was. He made his whereabouts known by tapping a message on a steam-pipe." "H'm," said the doctor, whose youthful appearance might not give a stranger a proper measure of his long and varied experience. "Nearly suffocated, too. He couldn't have lasted there much longer. His heart action is pretty weak even yet. Better have him removed to his bed, and kept there for the rest of the day, at least." At that moment Jerry came hurrying down the deck. He was visibly excited, but, unlike Slim, he did not forget that not only must a soldier never permit his feelings to run away with him, but that he must be equally mindful of respect for superiors. And so, even as two men carried Lieutenant Mackinson away, he remained standing at salute, waiting for the captain to recognize him with a return of the salute. "And now what?" asked the captain. Jerry stepped forward, with difficulty repressing his excitement. "I stepped out of the wireless room for only a few moments," he said. "When I returned I found this lying upon the table." He opened his left hand. In it lay a piece of light chain, both ends broken. "Beside it," he continued, "was this note." From his pocket he extracted a piece of paper, the edges of which were roughly torn. He handed it to the captain, who read aloud: "Let this be a warning that no further interference will be of avail." The captain looked from the note to the chain. There was no further word on the paper, and no signature. "I believe, sir," said Jerry, "that this is the rest of the chain which was attached to the iron cross torn from the man caught in the battery room." The senior officer of the vessel took from his pocket the cross, with its two bits of chain still dangling from it. He placed the ends to the chain which Jerry had found in the wireless room. "You are right," he said simply. And there could be no doubt about it. The captain's face clearly showed the worry on his mind. The ship's physician, who had been told all about the affair, immediately after Joe's discovery of, and battle with, the mysterious stranger, appeared equally anxious.