"Our major premises we find still to be correct," announced Eldridge in the coldly didactic manner characteristic of the man. "This unknown operator is at a distance; and probably at a height. One indication we did not take sufficiently into consideration--the fact that this instrument alone is capable of communication with the instrument of this individual." Percy Darrow for the first time began to show signs of attention. He dropped the legs of his chair to the floor and leaned forward. "That would indicate, gentlemen, that the instrument whose location we are desirous of determining is of a peculiar nature. What that nature is we have no means of determining accurately; but in conjunction with the fact that our previous experiments failed to locate Monsieur X, we may adopt the hypothesis that the wireless apparatus of that individual is not so delicately responsive as the average. In other words, the zone within which he may be found is in fact wider than we had supposed." Darrow leaned back against the wall and closed his eyes. Eldridge continued, explaining the means he had taken to determine more accurately the exact location of Monsieur X. CHAPTER XIX PERCY KEEPS VIGIL The morning of the third day after the failure of the search, and of the sixth since McCarthy's disappearance, had arrived. During that time Percy Darrow, apparently insensible to fatigue, had maintained an almost sleepless vigil. His meals Jack Warford brought in to him; he dozed in his chair or on the couch. Never did he appear to do anything. The very persistent quietude of the man ended by making its impression. To all questions, however, Darrow returned but the one reply, delivered always in a voice full of raillery: "I couldn't bear to miss a single step of Eldridge's masterly work." About half past nine of the morning in question, through the door to the wireless office, always half opened, somebody looked hesitatingly into the room. Instantly Darrow and Jack were on their feet and in the hallway. "Helen!" cried Jack. "What is it? Anything happened?" demanded Darrow. She surveyed them both amusedly. "You certainly look like a frowzy tramp, Jack," she told her brother judiciously, "and you need sleep," she informed Darrow. The young scientist bowed ironically, his long lashes drooping over his eyes in his accustomed lazy fashion as he realized that the occasion was not urgent. Helen turned directly to him. "When are you going to stop this?" she demanded. Darrow raised his eyebrows. "You needn't look at me like that. You said you could lay your hands on Monsieur X at any moment; why don't you do it?" "Eldridge is too amusing." "Too amusing!" echoed the girl. "All you think of is yourself." "Is it?" drawled Darrow. "Have you been out in the city? Have you seen the people? Have you seen men out of work? Families leaving their homes? Panic spreading slowly but surely over a whole city?"