Lightning

When he had the numbers and doubled-checked them, he entered them in the board. Carrying the submachine gun in one hand and the pistol in the other, he climbed into the gate and passed through the point of transmission—

— and returned to the institute.

He stood for a moment in the gate, surprised, confused. Then he stepped through the energy field again—

— and returned to the institute.

The explanation hit him with such force that he bent forward as if he actually had been punched in the stomach. He could not go back earlier now, for he had already showed up at that place five minutes after leaving it; if he went back now he would be creating a situation in which he would surely be there to see himself arrive the first time. Paradox! The mechanism of the cosmos would not permit a time traveler to encounter himself anywhere along the time stream; when such a jaunt was attempted, it invariably failed. Nature despised a paradox.

In memory he could hear Chris in the sleazy motel room where they had first discussed time travel: "Paradox! Isn't this wild stuff, Mom? Isn't this wild? Isn't this great?" And the charming, excited, boyish laughter.

But there had to be a way.

He returned to the programming board, dropped the guns on the work desk, and sat down.

Sweat was pouring off his brow. He blotted his face on his shirt-sleeves. Think. He stared at the Uzi and wondered if he could send that back to her at least. Probably not. He had been carrying the machine gun and the pistol when he had returned to her the first time, so if he sent either of the guns back four minutes and fifty seconds earlier, they would exist twice in the same place when he showed up just four minutes and fifty seconds later. Paradox.

But maybe he could send her something else, something that came from this room, something he had not been carrying with him and that would not, therefore, create a paradox. He pushed the guns aside, picked up a pencil, and wrote a brief message on a sheet of tablet paper: THE SS WILL KILL YOU AND CHRIS

IF YOU STAY AT THE CAR. GET AWAY. HIDE. He paused, thinking.

Where could they hide on that flat desert plain? He wrote: MAYBE IN THE ARROYO. He tore the sheet of paper from the tablet. Then as an afterthought he hastily added: THE SECOND CANISTER OF VEXXON. IT'S A WEAPON TOO.

He searched the drawers of the lab bench for a glass beaker with a narrow top, but there were no such vessels in that lab, where all of the research had been related to electromagnetism rather than to chemistry. He went down the hall, searching through other labs, until he found what he needed.

Back in the main lab, carrying the beaker with the note inside it, he entered the gate and approached the point of transmission. He threw the object through the energy field as if he were a man stranded on an island, throwing a bottled message into the sea.

It did not bounce back to him.

— but the brief vacuum was followed by a blustery inrush of hot wind tainted by the faintly alkaline smell of the desert.

Standing close at her side, holding fast to her, delighted by Stefan's magical departure, Chris said, "Wow! Wasn't that something, Mom, wasn't that great?"

She did not answer because she noticed a white car driving off state route 111, onto the desert floor.

Lightning flared, thunder shook the day, startling her, and a glass bottle appeared in midair, fell at her feet, shattering on the shale, and she saw that there had been a paper inside.

Chris snatched the paper from among the shards of glass. With his usual aplomb in these matters, he said, "It must be from Stefan!"

She took it from him, read the words, aware that the white car had turned toward them. She did not understand how and why this message had been sent, but she believed it implicitly. Even as she finished reading, with the lightning and thunder still flickering and rumbling through the sky, she heard the engine of the white car roar.

She looked up and saw the vehicle leap toward them as its driver accelerated. They were almost three hundred yards away, but were closing as fast as the rough desert terrain permitted.

"Chris, get both Uzis from the car and meet me at the edge of the arroyo. Hurry!"

As the boy sprinted to the open door of the nearby Buick, Laura raced to the open trunk. She grabbed the canister of Vexxon, lifted it out, and caught up with Chris before he had reached the brink of the deep, naturally carved water channel, which was a raging rivet during a flash flood but dry now. The white car was less than a hundred and fifty yards away. "Come on," she said, leading him eastward along the brink, "we've got to find a way down into the arroyo."