"But at about the fifty-mile limit of sending we lost him," objected Jack. "You mean at about two o'clock in the morning," amended Darrow. "Eh? Yes, it was about two. But how did he get on to what Eldridge was doing?" "He read it in the paper," replied Darrow. "At twelve the reporters left. At a little before two our enterprising friend, the _Despatch_, issued an extra in its usual praiseworthy effort to enlighten the late Broadway jag. Monsieur X read it, and knew exactly what was up." "How do you know?" "Because I read the extra myself." "But even then?" "Then he began to pay more attention. It was easy enough to fake when he knew what was doing. For all I know, he could hear Eldridge giving his directions." The company present ruminated over the disclosures thus far made. "About the City Hall affair?" asked Helen finally. "I used to sit where I could command the hall," said Darrow, "and, therefore, I was aware that Monsieur X never left his room. To make the matter certain, I powdered the sill of the door with talcum, which I renewed every day after the cleaners. You remember we got to talking very earnestly in the hall, so earnestly that I, for one, forgot to watch. When I realized my remissness, I saw that the powder on the sill had been disturbed, that Monsieur X had gone out. "My first thought then was to warn the people. To that end I was on my way to the _Despatch_ office when sheer chance switched me into the City Hall tragedy. I possessed myself of the apparatus--" "That was the square black bag!" cried Jack. "Of course--and hustled back to the Atlas Building. You can bet I was relieved when I found that Monsieur X had returned to his lair." "Talcum disturbed again?" asked Jack. "Precisely." "And the black bag?" "Contained merely a model wireless apparatus with a clockwork arrangement set to close the circuit at a certain time. That is why Monsieur X was not involved in his own catastrophe." "I see!" "Then all I had to do was to sit still and wait for him to become dangerous." "How did you dare to take such chances?" cried Helen. "I took no chances," answered Darrow. "Don't you see? If he were to attempt to destroy the city, he must either involve himself in the destruction, or he must set another bit of clockwork. If he had left his office again I should have seized him, broken into the office, and smashed the apparatus." "But he was crazy," spoke up Mrs. Warford. "How could you rely on his not involving himself in the general destruction?" "Yes, why did you act when you did?" seconded Helen.