_The ruby rolled across the table and...._ He was once again sitting before the Martian artifact, his eyes once again focussed on the ruby as it rolled across the table. Like something in a magician's act, he had disappeared from his position near the window and reappeared in the chair. As before, the cut on his hand stung painfully, but this time he ignored it and kept his eyes focussed on his wrist watch. It was eleven forty-five eastern standard time. * * * * * _The ruby rolled across the table...._ His eyes were no longer focussed on the watch, but he remembered that the hands had last indicated eleven fifty-five. And now they were back at _eleven forty-five_. He was trapped in a period of time only ten minutes long! He lit a cigarette with trembling fingers and tried to think calmly. What danger was there in a time trap? He felt no physical pain and so far the trap had only caused him small inconveniences. Anything he did during the ten-minute period was magically undone when he was thrown backward in time. He had put iodine on the cut on his hand and it had disappeared. He had walked to the window, but at the beginning of the next cycle, without any conscious sensation, he found himself sitting in the chair once more. But how could movement through time harm him? And was he the only one aware of the trap? He turned the television set on and watched a news announcer during several following cycles. Before long, he was convinced that he was the only one who was aware of the repeated time interval. The news announcer represented everyone in the world, and if he were conscious of the fact that he'd read the same news more than a dozen times, there would have been _some_ change in his expression! He recalled how the Martian had moved his fingers over the globe and how he'd felt a burning sensation inside his skull. The device had evidently been adjusted to his neural pattern so that only he was conscious of the trap. Or else only someone within a certain effective radius--fifty feet, for instance--was conscious of the repeated time intervals. Although he'd always believed the stories about the time machines and he now had proof of their existence, he still found it difficult to comprehend their operation. He had heard that such a machine concentrated on only a few atoms of a radioactive substance. By drawing energy from the space-time continuum itself, the machine succeeded in thrusting those atoms backward or forward in time, and since that affected the entire probability stream, all physical matter was forced to follow them through the time stream.