They moved silently across the room, taking their guns with them, toward the Machine, toward the silver metal and the roaring light.

First a day and then a night and then a day and then a night, then it was day-night-daynight. A week, a month, a year, a decade! A.D. 2055. A.D. 2019. 1999! 1957! Gone! The Machine roared.

They put on their oxygen helmets and tested the intercoms.

Eckels swayed on the padded seat, his face pale, his jaw stiff. He felt the trembling in his arms and he looked down and found his hands tight on the new rifle. There were four other men in the Machine. Travis, the Safari Leader, his assistant, Lesperance, and two other hunters, Billings and Kramer. They sat looking at each other, and the years blazed around them.

“Can these guns get a dinosaur cold?” Eckels felt his mouth saying.

“If you hit them right,” said Travis on the helmet radio. “Some dinosaurs have two brains, one in the head, another far down the spinal column. We stay away from those. That’s stretching luck. Put your first two shots into the eyes, if you can, blind them, and go back into the brain.”

The Machine howled. Time was a film run backward. Suns fled and ten million moons fled after them. “Think,” said Eckels. “Every hunter that ever lived would envy us today. This makes Africa seem like Illinois.”

The Machine slowed; its scream fell to a murmur. The Machine stopped.

The sun stopped in the sky.

The fog that had enveloped the Machine blew away and they were in an old time, a very old time indeed, three hunters and two Safari Heads with their blue metal guns across their knees.

“Christ isn’t born yet,” said Travis, “Moses has not gone to the mountains to talk with God. The Pyramids are still in the earth, waiting to be cut out and put up. Remember that. Alexander, Caesar, Napoleon, Hitler-none of them exists.” The man nodded.

“That”–Mr. Travis pointed–“is the jungle of sixty million two thousand and fifty-five years before President Keith.”

He indicated a metal path that struck off into green wilderness, over streaming swamp, among giant ferns and palms.

“And that,” he said, “is the Path, laid by Time Safari for your use. It floats six inches above the earth. Doesn’t touch so much as one grass blade, flower, or tree. It’s an anti-gravity metal. Its purpose is to keep you from touching this world of the past in any way. Stay on the Path. Don’t go off it. I repeat. Don’t go off. For any reason! If you fall off, there’s a penalty. And don’t shoot any animal we don’t okay.”

“Why?” asked Eckels.

They sat in the ancient wilderness. Far birds’ cries blew on a wind, and the smell of tar and an old salt sea, moist grasses, and flowers the color of blood.

“We don’t want to change the Future. We don’t belong here in the Past. The government doesn’t like us here. We have to pay big graft to keep our franchise. A Time Machine is finicky business. Not knowing it, we might kill an important animal, a small bird, a roach, a flower even, thus destroying an important link in a growing species.”

“That’s not clear,” said Eckels.

“All right,” Travis continued, “say we accidentally kill one mouse here. That means all the future families of this one particular mouse are destroyed, right?”

“Right”

“And all the families of the families of the families of that one mouse! With a stamp of your foot, you annihilate first one, then a dozen, then a thousand, a million, a billion possible mice!”

“So they’re dead,” said Eckels. “So what?”