“But why couldn’t they come back even earlier tonight, earlier than they came the first time, back to the house, and attack us before my guardian ever showed up to warn us?”
“Paradox,” the boy said. “You know what that means?” The word seemed too complex for a boy his age, but she said, “Yes, I know what a paradox is. Anything that’s self-contradictory but possibly true.”
“See. Mom, the neat thing is that time travel is full of all kinds of possible paradoxes. Things that couldn’t be true, shouldn’t be true—but then might be.” Now he was talking in that excited voice I with which he described scenes in his favorite fantastic films and comic books, but with more intensity than she had ever heard before, probably because this was not a story but reality even more amazing than fiction. “Like suppose you went back in time and married your own grandfather. See, then you’d be your own grandmother. If time travel was possible, maybe you could do that—but then how could you have ever been born if your real grandmother had never married your grandfather in the first place? Paradox! Or what if you went back in time and met up with your mom when she was a kid and accidentally killed her? Would you just cease to exist—pop!—like you’d never been born? But if you ceased to exist—then how could you have gone back in time in the first place? Paradox! Paradox!”
Staring at him in the moon-painted darkness of the Jeep, Laura felt as though she was looking at a different boy from the one she had always known. Of course, she had been aware of his great fascination with space-age tales, which seemed to preoccupy most kids these days, regardless of age. But until now she hadn’t gotten a deep look inside the mind shaped by those influences. Evidently the American children of the late twentieth century not only lived interior fantasy lives richer than those of children at any other time in history, but they seemed to have gotten from their fantasies something not provided by the elves and fairies and ghosts with which earlier generations of kids had entertained themselves: the ability to think about abstract concepts like space and time in a manner far beyond their intellectual and emotional age. She had the peculiar feeling that she was speaking to a little boy and a rocket scientist coexisting in one body.
Disconcerted, she said, “So . . . when these men failed to kill us on their first trip tonight, why wouldn’t they make a second trip earlier than the first, to kill us before my guardian warned us that they were coming?”
“See, your guardian already showed up in the time stream to warn us. So if they came back before he warned us—then how could he have warned us in the first place, and how could we be here where we are now, alive? Paradox!”
He laughed and clapped his hands like a gnome chortling over some particularly amusing side-effect of a magical spell.
In contrast to his good humor, Laura was getting a headache from trying to sort out the complexities of this thing.
Chris said, “Some people believe time travel isn’t even possible ’cause of all the paradoxes. But some believe it’s possible so long as the trip you make into the past doesn’t create a paradox. Now if that’s true, see, then the killers couldn’t come back on a second, earlier trip ’cause two of them had already been killed on the first trip. They couldn’t do it because they were already dead, and it was a paradox. But the guys you didn’t kill and maybe some new time travelers could make another trip to cut us oft at the end of this road.” He leaned forward to peer through the streaked windshield again. “That’s what all that lightning was off to the south when we were weaving to keep them from shooting us—more guys from the future were arriving. Yeah, I’ll bet they’re waiting for us down there somewhere, down there in the dark.”
Rubbing her temples with her fingertips, Laura said, “But if we turn around and go back, if we don’t drive into the trap ahead, then they’ll realize we’ve outthought them. And so they’ll make a third trip back in time and return to the Mercedes and shoot us when we try to drive back that way. They’ll get us no matter which way we go.”