"Did _you_ know I was going to my cousin's?" Joey asked surprised. She had never thought Professor Trouville would take half so much interest in what the schoolgirls did. He had never seemed to think anything about them, except that they were very stupid at chemistry. However, she had no time for wondering. "Please, where would you like me to start tidying?" she asked, looking round the big, untidy place. The Professor was bending over something on the table--a little square wooden box, into which he appeared to be fitting a small glass tube with care. He did not even look up. "I need many bottles from the closet," he said. "Shall I get them?" asked Joey politely. She dived into the innermost recesses of the closet. As she did so she heard quick steps across the floor, and the closet door slammed, making the place quite dark. Joey was startled by the suddenness of the slam and darkness; but she dared not move for fear of stumbling over the bottles that littered the floor. "Oh, please open the door--I can't see anything," she called, and as she called it the key turned in the lock. "Don't do that, please; I'm inside," she shouted at the top of her voice; but even while she called that fact out confidently there was an unbelievable fear looking over her shoulder--she felt she would see it, if she turned her head--and the knowledge that the Professor knew she was there all the time, and had locked her in on purpose. She put all the courage that was in her into the effort to push that horrid thought away. "If you're playing a trick on me, please stop it now, because there's a lot of tidying and Miss Conyngham will be fearfully vexed if I haven't changed my frock before my cousin sends for me," she urged. "They'll look for me if I'm not there when the car comes." She talked into thick darkness and silence. She could hear the Professor moving about the room, but he returned no answer at all. She spoke into a blank wall. The keyhole was still blocked with the key. She could see nothing, and what little she heard gave her no help at all. Still she tried hard to keep her end up. "I wish you'd stop it now and let me out," she said firmly. "If it's a joke you've had the best of it, and if it's a punishment I should like to know what I've done. Anyhow, I don't see staying here." The Professor came across to the closet; there was a little rattle, and the keyhole showed light. He had taken out the key, but he had not turned it.