"Pardon me," drawled Darrow, "they have been determined--or at least their controlling power." "In what way, may I ask?" inquired Professor Eldridge formally. "Very simply. By the exercise of a little reason. I am going to tell you, because I want you to start fairly with me; and because you'll know all about it in the morning, anyway." "Your idea--the one you told us yesterday--is to be published?" cried Helen, leaning forward with interest. "The basis of it will be," replied Darrow. "Now"--he turned to Eldridge--"listen carefully; I'm not going to indulge in many explanations. Malachi McCarthy, political boss of this city, has made a personal enemy of a half-crazed or at least unbalanced man, who has in some way gained a limited power over etheric and other vibrations. This power Monsieur X, as I call him--the Unknown--has employed in fantastic manifestations designed solely for the purpose of frightening his enemy into leaving this country." Eldridge was listening with the keenest attention, his cold gray eyes glittering frostily behind their toric lenses. "You support your major hypothesis, I suppose?" he demand calmly. "By wireless messages sent from Monsieur X to McCarthy, in which he predicts or appoints in advance the exact hour at which these manifestations take place." "In advance, I understand you to say?" "Precisely." "The proof is as conclusive for merely prophetic ability as for power over the phenomena." "In formal logic; not in common sense." Eldridge reflected a moment further, removing his glasses, with the edge of which he tapped methodically the palm of his left hand. Helen had sunk back into the depths of her armchair, and was watching with immobile countenance but vividly interested eyes the progress of the duel. "Granting for the moment your major hypothesis," Eldridge stated at last, "I follow your other essential statements. The man is unbalanced because he chooses such a method of accomplishing a simple end." "Quite so." "His power is limited because it has been applied to but one manifestation of etheric vibration at a time; and each manifestation has had a defined duration." Darrow bowed. "You are the only original think-tank," he quoted Hallowell's earlier remark. "You are most kind to place me in possession of these additional facts," said Eldridge, resuming his glasses, "for naturally my conclusions, based on incomplete premises, could hardly be considered more than tentative. The happy accident of an acquaintance with the existence of these wireless messages and this personal enmity gave you a manifest but artificial advantage in the construction of your hypothesis." "Did I not see you in the corridor of the Atlas Building the day of the first electrical failure?" asked Darrow. "Certainly." "Then you had just as much to go on as I did," drawled Darrow, half closing his eyes. The long dark lashes fell across his cheek, investing him in his most harmless and effeminate look. "I fail to--"