But it had happened. Elvin could visualize only two plausible explanations: mass insanity or mass hypnosis. Hypnosis! A sluggish relay clicked in his mind. He remembered a book. One of the tenth graders had been reading it--_Hypnotism in Theory and Practice_. Everything seemed clear after that. The tenth grade was an obstreperous bunch of unsocial adolescents. Somehow they had stumbled upon hypnotism and learned how to use it. The time for an accounting had come. Because of where Elvin lived, he was admirably situated to break the Schermerhorn twins first; and they were, perhaps, the weakest members of the group. He would have them alone, without the support of their peers. It would be easy. After all, he was a mature adult; they were still children. Once he had a confession from them, it would only be a minor operation to clear up the whole mess. When he reached the Schermerhorn ranch, dinner was on the table. He had no time to talk to the twins until afterward. Both David and Donald bolted the meal and rushed back to their workshop behind the garage. Their usual bad manners, Elvin realized, but what else could be expected? * * * * * Elvin finished a leisurely pipe in the living room, and then sauntered out to the boys' workshop. Surprisingly, the door was locked, the windows thickly curtained; they had never taken such precautions before. He knocked and, after a long wait, both David and Donald came outside to talk to him. They were naked to the waist and their husky, tanned bodies gleamed with sweat. A smudge of grease was smeared over David's unkempt blond hair. "Working on your car, boys?" Elvin inquired indulgently. He knew the technique. Put them at their ease, first; then come to the point when their guard was down. "Well, not exactly, Mr. Elvin." Donald said. "Mind if I watch? I always say I can learn as much about motors from you two as you learn from me about grammar." Neither of the twins said anything. After an uncomfortable silence, Elvin cleared his throat pointedly. He had never met with such disrespect. If they were his kids, they would long ago have been taught proper courtesy for their superiors! To fill the lengthening void, he asked. "What did you think of the little test I gave this morning?" "It was all right," Donald said. "You both did pretty well; I'm proud of you." "We had everything right," David pointed out without a flicker of expression. Elvin couldn't seem to engineer the dialogue as he used to. In that case, this was as appropriate a time as any for the question he had come to ask. He spoke slowly, with a tone of disinterest. "Do either of you know anything about hypnotism?" As a shocker, Elvin realized, it left much to be desired; their faces told him nothing. "A little," David volunteered. "We read eight or nine books on it over the weekend," Donald added. "That's a lot of reading. It must have taken a great deal of time." "Oh, a couple of hours."