All three rose. The operator was busy crashing away at his Leyden jars. "What next?" asked Jack. "That depends on two things." "Whether or not McCarthy takes the _Celtic_," interposed Hallowell quickly. "And whether Monsieur X will be satisfied with his mere disappearance, if he does not take the _Celtic_," supplemented Darrow. "In any case, we've got to find him. He's unbalanced; he possesses an immense and disconcerting and a dangerous power; he is becoming possessed of a _manie des grandeurs_. You remember the phrasing of his last message? 'I am your lord and master, and my wrath shall be visited on you. Begone!' That is the language of exaltation. Exaltation is not far short of irresponsible raving." "What possible clue--" began Jack Warford blankly. "When a man is somewhere out in the ether there is no clue," replied Darrow. "Then how on earth can you hope to find him?" "By the exercise of pure reason," said Darrow calmly. CHAPTER XIII DARROW'S CHALLENGE With a final warning to Simmons as to the dissemination of any information without consulting him, Darrow left the room. Hallowell listened to this advice with unmixed satisfaction; the afternoon papers would not be able to get at his source of information. The reporter felt a slight wonder as to how Darrow had managed his ascendency over the operator. An inquiry as to that met with a shake of the head. "I may have to ask your help in that later," was his only reply. At the corner, after pushing through a curious crowd, the men separated. Hallowell started for the wharf; Jack Warford for home--at Darrow's request. The scientist returned to his own apartments, where he locked himself in and sat for five hours cross-legged on a divan, staring straight ahead of him, doing nothing. At the end of that time he cautiously stretched his legs, sighed, rose, and looked into the mirror. "I guess you're hungry," he remarked to the image therein. It was now near mid-afternoon. Percy Darrow wandered out, ate a leisurely meal at the nearest restaurant, and sauntered up the avenue. He paused at a news stand to buy an afternoon paper, glanced at the head-lines and a portion of the text, and smiled sweetly to himself. Then he betook himself by means of a bus to the Warford residence. Helen was at home, and in the library. With her was Professor Eldridge. The men greeted each other formally. After a moment of general conversation Darrow produced the newspaper. "I see you have your theories in print," he drawled. "Very interesting. I didn't know you'd undertaken grammar-school physics instruction." "I know I'm going to be grateful for any sort of instruction--from anybody," interposed Helen. "I'm all in the dark." "Like the Atlas Building," Darrow smiled at her. "Well, here's a very good exposition in words of one syllable. I'll leave you the paper. Professor, what have you concluded as to the causes?" "They are yet to be determined."