Dan whirled. His fist shot out. There was a scream of machinery, then a crash and a clatter. An imitation monster with a huge jaw and giant teeth lay on its back on the floor. Milbun let out a slow whistle. "_Dismounted_ it. Boy!" "A one-bite, too," breathed Mavis. Mrs. Milbun came over and looked at Dan approvingly. Dan had been about to apologize, but checked himself when the others smiled cheerfully and went back to what they were doing. This consisted of dodging, tricking or outrunning the various contraptions that lunged at them, chased them, tripped them, trailed, stalked and sprang out at them from nearly every place in the room. Finally the gym began to fill up with other people. The Milbuns got ready to leave and Dan followed. * * * * * Dan lay in his bed that night and tried to summarize the points he didn't understand. First was the question of vacation. But he supposed he would learn about that tomorrow. Next was "charge." Apparently one went on vacation when his "charge" was low, because the vacation advisor had said, "The family put their vacation off for her, and as a result their charge has run very low." But just what was "charge"? Dan remembered the flickering bulb in the store window, ringed by the words "Your Corrected Charge--Courtesy of Save-Your-Life Co." Apparently he had _some_ charge, because the bulb had flickered. But where did he get it? Then he thought of the waterfront and of the little boy caught at the hole. What was the point of that? And why did that produce such an uproar when, a little later, a grown man could get dragged out of sight on a well-traveled street and never cause a single notice? Dan felt himself sinking into a maze of confusion. He dismissed the problems and went to sleep clinging to one fact. The Porcyns _must_ be honest people who would keep an agreement, once made. On what other planet could anyone find a slot machine with no slot, but just an open box for the money? Dan fell asleep, content that he had the answer to that part of the problem, at least. Before it was light, he awoke to an odd familiar buzz inside his head. "Dan," said Kielgaard's voice, small and remote. Dan rolled over, lay on his back and spoke sub-vocally. "Right here." "Can you talk?" "Yes," said Dan, "if I can stay awake." "Can you give us a summary?" "Sure." Dan told him briefly what had happened. Kielgaard was silent a moment. Then he said, "What do you think 'charge' is?" "I haven't been in any condition to think. Maybe it's a surgically implanted battery, set to run down after so long." "Too clumsy. What about radioactivity?" "H'm. Yes, you mentioned a mine on the inner planet. Maybe they mine radioactive ore. That would explain why I have _some_ charge. There's residual radioactivity even in the atmosphere of Earth."