His toss was good. The knife fell over the key, and again he drew it to him. To his disgust, the key had not moved. Again and again he tried it, but the knife slid over the key without moving it. He looked more carefully and saw that the key was caught on an obstruction in the flooring. With careful aim, he threw his knife so as to drive the key further away. He threw the knife again and tried to draw the key to him from its new position. It came readily until it reached the inequality in the floor which had stopped it the first time. All of his efforts to draw it nearer were fruitless. He give vent to a muttered oath as he looked at the clock. Thirty minutes of his time had gone. A second time he knocked the key away and strove to draw it to him with no success. The clock bore witness to the fact that another ten minutes had been wasted. He rose to his feet and carefully surveyed his surroundings. A cry of joy burst from his lips. On the floor was a tiny metallic thread which he knew for a wire. He bent down and picked it up. It was fine and very flexible. He doubled it three times and strove to bend a hook in it. The wire was too short to offer much hope, but he threw himself prone and began to fish for the key. The wire reached it readily enough, but it did not have rigidity enough to pull the key over the little bump which held it. A glance at the clock threw him into an agony of despair. A full hour had passed since Saranoff had left him. Carnes might even now be walking into the trap which had been laid for him. He rose to his feet and thought rapidly, twisting the wire idly around the knife as he did so. He glanced at the work of his hands, and an oath broke from his lip. "Fool!" he exclaimed. "I deserve to die! The means for liberation were in my hands all the time." * * * * * With feverish activity, he ripped open the flashlight. He held the two ends of the wire against the terminals of the light battery and touched the knife to his steel key ring. To his joy, the ring adhered to the knife. Under the influence of the battery, the wire-wrapped knife had become a small electromagnet. In a moment the doctor was prone on the floor. He tossed the knife out to the key. His aim was good and it fell directly beyond. With trembling hands he drew the knife toward him. It reached the key. Scarcely daring to breathe, he pulled it closer. The key had risen over the ridge which had held it, and was adhering to the knife. In another moment, he stood erect, freed from the shackles which had bound him. He made for the door at a run, but a sudden thought stopped him. The clock showed him that an hour and twenty minutes had passed. "Carnes must be nearly here!" he cried. "If I go blundering out, I'm liable to run right into the trap they have laid for him, and then we're both gone. If I yell to warn him, the fool will come ahead at full tilt. What the dickens can I do?"