The outer door jerked open, and Jack Warford leaped into the room, revolver in hand. Darrow called an instant warning. "All right!" he shouted. "Turn on the light, next to you somewhere. Shut the door." These orders were obeyed. The electric flared. By its light the office was seen to be quite empty save for a cabinet full of books and papers; rows and rows of battery jars; the receiving and sending apparatus of a wireless outfit; the deal table, and one wooden chair. Darrow looked around keenly. "That's all right, Jack," said he. "Just get around here cautiously and raise the window shade. Look out you don't get near that table. That's it. Now just help me get this man a little away from the table! Good! Now, tie him up. No, bring over the chair. Tie him in that chair. Gently. That's all right. Whew!" "You're hurt," said Jack. Darrow touched his forehead. "A bump," he said briefly. "Well, Jack, my son, we've done it!" "You don't mean to say--" cried Jack. Darrow nodded. "Now, my friend," he addressed the huddled figure in the chair, "the game is up. You are caught, and you must realize it." He surveyed the captive thoughtfully. "Tell me, who are you?" he added. "I should know you, for you are a great discoverer." The old man stared straight at his interlocutor with his expressionless eyes, behind which no soul, no mind, no vitality even seemed to lie. Darrow asked him several more questions, to which he received no replies. The man sat like a captured beast. "I'm sorry," said Darrow to Jack. "I should like to have talked with him. Such a man is worth knowing; he has delved deep." "He'll talk yet, when he gets over his grouch," Jack surmised. But Darrow shook his head. "The man is imbecile," he said. "He has been mentally unbalanced; and his disorder has grown on him lately. When I drove back his wrist just now the cord snapped in his brain." Jack turned to stare at the captive. "By Jove, I believe you're right!" said he at last. Darrow was standing looking down on the deal table. "Come here, Jack," said he. "I want you to look at the deadliest engine of destruction ever invented or wielded by mortal man. I suspect that if you were to reach out your hand and hold down the innocent-looking telegraph key there you would instantly destroy every living creature in this city." Jack turned a little pale, and put both hands behind him. Darrow laughed. "Feel tempted?" he inquired. "Makes me a little dizzy, like being on a height," confessed Jack. "How's the trick turned?" "I don't know," said Darrow. "I'm going to find out if I can." Without attempting to touch anything, he proceeded to examine carefully every detail of the apparatus.