The boy's feelings were mixed. He wanted to stay. These people interested him and there were a hundred mysteries to solve,--living skeletons, eyes blinking from the walls, self-opening doors, lights that gleamed and clocks that buzzed. A fresh mystery was added when five minutes later the girl pressed a second button and a tray laden with cups, saucers, a plate of cakes and a pot of steaming cocoa appeared. "The 'Eye' did it for us," the professor explained in a matter-of-fact tone. "In these days one scarcely needs a servant even when he is able to afford one." Perhaps Johnny would have said, "What is the 'Eye'?" but at that moment the door at the rear opened and a tall youth with tumbled red hair appeared. The professor rose. "Son, meet Johnny Thompson. Now we are all here." When, two hours later, Johnny left this place of enchantment, his head was in a whirl. "Just goes to show," he chuckled to himself, "that when you do an unusual stunt anything may happen--just anything at all." Several things _had_ happened in the last two hours. He had come to have a high regard for the professor and his family. He had received payment in full for the professor's library and a ten dollar bill thrown in for good measure. "Boy alive!" the professor had exclaimed when he hesitated to accept this extra ten. "If some shark that haunts those auctions had got my books it would have cost me a small fortune to redeem them." All this had happened, and much more. "Best of all," Johnny whispered to himself, "I am no longer alone. I've made a place for myself." Just what sort of place it was, he did not surely know. "I should like to have you cast in your lot with us," the professor had said. "A boy who thinks of others, as you have done in this library affair, is sure to be of service anywhere. "We do strange and interesting things here." The professor's eyes had twinkled. "Sometimes they are useful and practical; sometimes they are not. Always they are absorbing, at times quite too startling. At times we have money, at others none. Just now we are quite rich." He chuckled. "Someone offered us a great deal of money for an electric contraption that sorts beans, sorts a car load a day. Who wants that many beans?" He chuckled again. "Anyway we have money and they can sort beans. Money means material, equipment for fresh experiments. You will come with us?" He squinted at Johnny. "Yes. Yes, sure." Johnny scarcely knew what leg he was standing on. "Queer business!" was his mental comment. "We will exact only one promise," the professor continued. "You'll not pry into our secrets. Such secrets as we entrust to you you will divulge to no man. Do you promise?" "I promise." "You'll learn a lot and enjoy the work a heap," the son had said to Johnny.