The mouse was no fool. He inspected the wire tunnel carefully. Three of his brothers had been taken away by various metal contrivances and he was not going to follow them if he could help it. The mouse sniffed the wires, climbed the top of the little cage and raced around it, poking it and bumping it. Often a trap could be sprung by poking it with a foot--just jarring it. That left the bait safe to eat. But this seemed innocuous. No springs, no wires, no trapdoor, no mirrors. Just a little tunnel of wire cloth about six inches long and two inches in diameter. The mouse entered the tunnel; headed for the bit of bacon. Nothing happened, and the mouse gathered speed. It paid no attention to the silvery metal ring that encircled the inside of the tunnel, and would not have known what it was anyway. There were other things there, too. Bits of Alnico V, a couple of cubes of Cerise Wax, some minute inductances and a very small capacitor made of a tiny square of mica with some silver sputtered on both sides. Down in the center was a clear crystal with electrodes clamped on it. The whole assembly was about a half inch cubed and from it on either side emerged the ends of the silvery-wire loop. Had the mouse seen all this, it would not have understood. That was not strange, for even the man who built it was not too certain what it did, or what it was, nor how it worked. He knew it worked, and it served its purpose. He was like the man who daily uses electricity enough to kill him, but is not quite sure of what goes on in the instant between his snap of the switch and the arrival of the illumination. The mouse cared not. All he was after was food. He paused, uncertainly and checked to see if there were any moving parts. There were, but they were intangible fields and stresses of space. Then the mouse raced forward and passed through the silvery circle. But did not come out on the far side. A second mouse, watching, took a sigh of relief. The bait was still there. There had neither been cry of pain nor was there a captive warning the rest away in mouse-ese. He, too, came to the trap, and entered, the odor from the rancid bacon drawing him with a magnetic force. He, too, came to the silvery circle, passed through--into nothingness! Came then another, and another, each pleased in turn that the bait was his alone for the taking. And as each one entered and disappeared, a tiny silent counter moved one digit higher. Came morning.... And-- "Great Unholy Madness," exploded Peter. "If this is a rat-proof building, I am a Chinese policeman!" Jack Brandt looked over Peter's shoulder. "How many?" he asked. "Twenty-three!" "Golly," grinned Brandt. "We're outnumbered." "We won't be long if this thing works like this every night. This is better than the original ball-bearing mousetrap." "Which?" Peter grinned. "The tomcat," he said. * * * * *