He felt an almost irresistible desire to find his way out of the place and make a dash for it. But there were the books. He must manage to get his money back somehow. He had hoped the professor might be able to pay him the money and take the library. "Cost hundreds of dollars in the first place, those books," he murmured. "You'd think--" Again he broke off to listen and stare. Strange noises, curious flashes of light, and then the door swung open. The golden-haired girl appeared. The door closed behind her. "He--he'll be here soon." She seemed breathless. "He--he's working at something, a--a sort of trap. Do you know," she whispered, "this is a terrible neighborhood--truly frightful! That is why we live here." "Curious sort of reason," the boy thought, but he said never a word, for at that instant the clock-like affair on the wall began buzzing loudly, the red light blinked six times in quick succession. "Oh!" There was consternation in the girl's voice. Seizing the astonished boy by the arm, she dragged him to a corner of the room. There he found himself looking at what appeared to be a narrow strip of mirror. Upon that mirror moving objects began to appear. Before his astonished eyes these spots arranged themselves into the form of two skeletons, one tall, one short. Dangling from the hip-bone of the tall skeleton was what appeared to be a long knife. Again the girl whispered, "Oh!" But the short skeleton! Trembling so it appeared to dance, it slipped a knife along its bony wrist to at last grip it firmly in its skeleton fingers. The girl touched a button here, another there. The thing on the wall buzzed. Words were spoken outside the door, indistinct words. The skeletons disappeared. There came the sound of a door closing. "They--they're gone!" The girl sighed. Catching a slight sound of movement behind him, Jimmy whirled about to find himself looking into a pair of smiling blue eyes. "Here," he thought to himself, "is the girl's father, the professor." There were the same features, the same shock of golden hair. "I am Professor Van Loon," the man said in a voice that was low, melodious and dreamy. "Beth here tells me you bought my books," he went on. "That was kind of you. We've been moving about a great deal. The books have followed us here and there. Charges piled up. Until quite recently money has been scarce. Then, I confess, I forgot. In these days one is likely to forget his choicest treasures." He turned to the girl. "Beth, who was at the door just now?" "Two men." She trembled slightly. "They carried knives, so I opened the door on the outside. They--they hurried away." "I dare say!" The professor chuckled dryly. "Press the button, Beth," the professor said, nodding his head toward the right wall. "Our guest will stay for cocoa and cakes, I am sure. That right?" he asked, turning to Johnny. "I will, yes," Johnny agreed. The girl pressed a button like a lamp switch in the wall.