hour. No, there'd be slip-ups."

Pete considered it, pouring more wine. "An idea—but you're right, maybe. I haven't tried going back—if I'd sent the dog backwards, I couldn't have checked up on it, while I could be waiting in the future. Okay, you've convinced me."

"Then you're not going in the contraption."

Pete's laughter was spontaneous and loaded with amusement. "I'm going forward and find out why no one has come back! I've got a nice collection of rare coins I can trade off up there—should be more valuable—and I'll bring you back a working invention from the next century. With luck, I'll bring you the answer. And after that, maybe I can go back and kill an ancestor, just to see what happens."

"Don't be a fool!"

But Pete was grinning, and opening the door to the cage that rested in the middle of his laboratory. "Fifty years this trip," he said, spinning the dials. "And you won't have long to wait; I'll come back just about in no time."

Ned started to yell something, but there was a curious flicker, such as he'd seen when Pete sent the dog forward. The time machine blurred over, its surface seeming to stretch into infinity while contracting to nothing at the same time.

Then it was gone. Ned groped for the wine bottle, cursing, and drained the contents. Then he sat down to wait.

Three days later, the police came looking for Pete, on some mysterious tip, probably from a fellow worker. It was a pretty rough time, for a while, though they finally decided it was just another mystery, and that Ned's yarn of having been there only to keep an appointment was true. Ned had influential friends, even if he didn't have money, then.

For three years, he rented Pete's laboratory, before he made enough to buy it. For a decade, he lived in it; but by then he'd begun to know that Pete wasn't coming back.

"The building's still there," Old Ned finished. "The diagrams of his machine are still in the drawers. But Pete never showed up. I tell you, keep your fool grandson out of time machines, Lem. They don't work. Too many paradoxes—if they'd work, you could steal a future invention, get credit for inventing it, and nobody would ever have to invent it. When things have that many angles that can't work, the thing itself can't work."

Lem shook his 

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