was correct) would have landed them at the end of the Wisconsin glacial period; two jumps, at its beginning. The third would set them down toward the end of the Sangamon Interglacial and apparently it had—give or take ten thousand years or so.

They had arrived at a time when the climate did not seem to vary greatly, either hot or cold. The flora was modern enough to give them a homelike feeling. The fauna, modern and Pleistocenic, overlapped. And the surface features were little altered from the twentieth century. The rivers ran along familiar paths, the hills and bluffs looked much the same. In this corner of the Earth, at least, 150,000 years had not changed things greatly.

Boyhood dreams, Hudson thought, were wondrous. It was not often that three men who had daydreamed in their youth could follow it out to its end. But they had and here they were.

Johnny was on watch, and it was Hudson's turn next, and he'd better get to sleep. He closed his eyes, then opened them again for another look at the unfamiliar stars. The east, he saw, was flushed with silver light. Soon the Moon would rise, which was good. A man could keep a better watch when the Moon was up.

He woke suddenly, snatched upright and into full awareness by the marrow-chilling clamor that slashed across the night. The very air seemed curdled by the savage racket and, for a moment, he sat numbed by it. Then, slowly, it seemed—his brain took the noise and separated it into two distinct but intermingled categories, the deadly screaming of a cat and the maddened trumpeting of a mastodon.

The Moon was up and the countryside was flooded by its light. Cooper, he saw, was out beyond the watchfires, standing there and watching, with his rifle ready. Adams was scrambling out of his sleeping bag, swearing softly to himself. The cooking fire had burned down to a bed of mottled coals, but the watchfires still were burning and the helicopter, parked within their circle, picked up the glint of flames.

"It's Buster," Adams told him angrily. "I'd know that bellowing of his anywhere. He's done nothing but parade up and down and bellow ever since we got here. And now he seems to have gone out and found himself a saber-tooth."

Hudson zipped down his sleeping bag, grabbed up his rifle and jumped to his feet, following Adams in a silent rush to where Cooper stood.

Cooper motioned at them. "Don't break it up. You'll never see the like of it again."

Adams brought his rifle up.

Cooper knocked the barrel down.

"You fool!" he shouted. "You want them turning on us?"

Two hundred yards away stood the mastodon and, on his back, the screeching saber-tooth. The great beast reared into the air and came down with a jolt, bucking to unseat the cat, flailing the air with his massive trunk. And as he bucked, the cat struck and struck again with his gleaming teeth, aiming for the spine.

Then the mastodon crashed head downward, as if to turn a somersault, rolled and was on his feet again, closer to them now than he had been before. The huge cat had sprung off.

For a moment, the two stood facing one another. Then the tiger charged, a flowing streak of motion in the moonlight. Buster wheeled away and the cat, leaping, hit his shoulder, clawed wildly and slid off. The mastodon whipped to the attack, tusks slashing, huge feet stamping. The cat, caught a glancing blow by one of the tusks, screamed and leaped up, to land in spread-eagle fashion upon Buster's head.

Maddened with pain and fright, blinded by the tiger's raking claws, the old mastodon ran—straight toward the camp. And as he ran, he grasped the cat in his trunk and tore him from his hold, lifted him high and threw him.

"Look out!" yelled Cooper and brought his rifle up and fired.

For an instant, Hudson saw it all as if it were a single scene, motionless, one frame snatched from a fantastic movie epic—the charging mastodon, with the tiger lifted and the sound track one great blast of bloodthirsty bedlam.

Then the scene dissolved in a blur of motion. He felt his rifle thud against his shoulder, knowing he had fired, but not hearing the explosion. And the mastodon was almost on top of him, bearing down like some mighty and remorseless engine of blind destruction.

He flung himself to one side and the giant brushed past him. Out of the tail of his eye, he saw the thrown saber-tooth crash to Earth within the circle of the watchfires.

He brought his rifle up again and caught the area behind Buster's ear within his sights. He pressed the trigger. The mastodon staggered, then regained his stride and went rushing on. He hit one of the watchfires dead center and went through it, scattering coals and burning brands.

Then there was a thud and the screeching clang of metal.

"Oh, no!" shouted Hudson.

Rushing forward, they stopped inside the circle of the fires.

The helicopter lay tilted at a crazy angle. One of its rotor blades was crumpled. Half across it, as if he might have fallen as he tried to bull his mad way over it, lay the mastodon.

Something crawled across the ground toward them, its spitting, snarling mouth gaping in the firelight, its back broken, hind legs trailing.

Calmly, without a word, Adams put a bullet into the head of the saber-tooth.

V

General Leslie Bowers rose from his chair and paced up and down the room. He stopped to bang the conference table with a knotted fist.

"You can't do it," he bawled at them. "You can't kill the project. I know there's something to it. We can't give it up!"

"But it's been ten years, General," said the secretary of the army. "If they were coming back, they'd be here by now."

The general stopped his pacing, stiffened. Who did that little civilian squirt think he was, talking to the military in that tone of voice!

"We know how you feel about it, General," said the chairman of the joint chiefs of staff. "I think we all recognize how deeply you're involved. You've blamed yourself all these years and there is no need of it. After all, there may be nothing to it."

"Sir," said the general, "I know there's something to it. I thought so at the time, even when no one else did. And what we've turned up since serves to bear me out. Let's take a look at these three men of ours. We knew almost nothing of them at the time, but we know them now. I've traced out their lives from the time that they were born until they disappeared—and I might add that, on the chance it might be all a hoax, we've searched for them for years and we've found no trace at all.

"I've talked with those who knew them and I've studied their scholastic and military records. I've arrived at the conclusion that if any three men could do it, they were the ones who could. Adams was the brains and the other two were the ones who carried out the things that he dreamed up. Cooper was a bulldog sort of man who could keep them going and it would be Hudson who would figure out the angles.

"And they knew the angles, gentlemen. They had it all doped out.

"What Hudson tried here in Washington is substantial proof of that. But even back in school, they were thinking of those angles. I talked some years ago to a lawyer in New York, name of Pritchard. He told me that even back in university, they talked of the economic and political problems that they might face if they ever cracked what they were working at.

"Wesley Adams was one of our brightest young scientific men. His record at the university and his war work bears that out. After the war, there were at least a dozen jobs he could have had. But he wasn't interested. And I'll tell you why he wasn't. He had something bigger—something he wanted to work on. So he and these two others went off by themselves—"

"You think he was working on a temporal—" the army secretary cut in.

"He was working on a time machine," roared the general. "I don't know about this 'temporal' business. Just plain 'time