his brain. But ultimately, it did not matter. He was going to die, to die in great pain. It wasn't fair that the rest of the world should go right on living, enjoying the life that Jason Wall had barely begun to taste. They'd see an article in the newspaper, perhaps. Famous Tycoon Dies. In a day, a week, they would forget. They would go on living out their little lives, enjoying their little enjoyments. But the sum total of them—three billion men, women, and children on Earth, was it?—added up to considerable enjoyment. Jason Wall envied them with a desperate, passionate envy.

When his thinking evolved to the next stage, he knew with petty triumph that only Jason Wall would have taken that step. He had an incurable disease. He was going to die. But the world would go right on, generations after generations. It wasn't fair. They had no right to enjoy what he, Jason Wall, would lose forever.

He toyed—seriously toyed for some weeks—with the idea of destroying the world. It could be done: he never doubted it for a minute. To develop the atomic bomb, the governments of the free world had pooled their resources in a crash program costing two billion dollars, and had succeeded in a very few years. Two billion dollars—that was the kind of figure Jason Wall understood. For two billion dollars, couldn't he hire all the world's top scientists to build a super-bomb which would utterly destroy Earth?

He could, of course. In theory, such a crash program, with Jason Wall's money and industrial know-how behind it, was a possibility. But for another reason, for a very simple reason, it was quite obviously impossible.

The scientists wouldn't do it.

Suicide? Never. He decided that firmly, two months after the prognosis. World-destruction? Impossible. Then what?

It was Eve who, trying to flaunt an intellectual prowess she really did not have, told him about time travel. There was this article she had read in the newspaper Sunday supplement, about the possibility of moving backwards through time. There was absolutely no natural law which said it could not be done, the article said. It was merely a question of probability. For, while in theory time travel was possible, it was practically impossible—unless, as the article suggested and Jason Wall thought in triumph, you pushed it. If you pushed it, the improbability became a possibility, then a probability, then a reality.

Crash program, he thought.

The world was made of particles. All reality, particles. Discreet particles of matter, of time, of space-time. Building blocks of the universe. Now, take these particles; and return them to the positions they occupied a moment ago—and you travel into the immediate past. Re-arrange them into the positions they occupied years ago, decades, generations, aeons—and you have time travel.

Crash program. Billions of dollars, he thought. All the world's great physicists. It could be done. He could do it.

But—so what?

Jason Wall smiled. It was the way his mind often functioned. Decide on something, apparently without relation to your problem. Then use it.

He couldn't have the world destroyed, despite his money and the decided possibility of instituting a crash program to do it. He wouldn't be able to fool the scientists, and the scientists just wouldn't do it.

But a crash program for time travel, now that was something else. That could be done. He would see that it was done.

For what purpose?

To return to the dawn of the human race. To find dawn man, the first man. Call him Adam. To find the first truly human being.

To kill him.

To snuff humanity out at its source, as a flame is snuffed before it can start a fire.

To prevent the human race from enjoying what he would never enjoy. To destroy humanity by killing the first man.

Of course, he told himself, that would obliterate, along with the rest of mankind's history and comedy and tragedy, the first forty-five years of his own life. But