"But you did see this shadow of probability?" rumbled Kingsley.

"Yes," said the Engineer, "I saw it very plainly. So plainly that I am tempted to believe it may be an actuality in time to come. But of that I cannot be sure. As I said, it may not exist, may never exist — at least to an extent where we could reach it — where it would have any bearing on our lives."

"There is a chance, though, that we could reach it?" asked Gary.

"There is a chance," said the Engineer.

"Then," said Herb, impatiently, "what are we waiting for?"

"But," said Gary, "if the universe is destroyed, if we should fail and the universe be destroyed, would that probability still be there? Wouldn't the fact that you saw it prove that we will find some way to save the universe?"

"It proves nothing," said the Engineer. "Even were the universe destroyed, the probability would still exist, for the world could have been. Destruction of the universe would be a factor of accident which would eliminate actuality and force all lines of probability to remain mere probability."

"You mean," breathed Caroline, "that we could go to a world which exists only as a probable world line and get information there to save the universe — that even after the universe is destroyed, if we fail and it is destroyed, the information which might have saved it still could be found, but too late, of course, to be of any use to us, on that probable world?"

"Yes," said the Engineer, "but there would be no one to find it then. The solution would be there, never used, at a time when it would be too late to use it. It is so hard to explain this thought as it should be explained."

"Maybe it's all right," said Herb, "but I crave action. When do we start for this place that might not be there when we get where we headed for?"

"I will show you," said the Engineer.

They followed him through a maze of laboratory rooms until they came to one which boasted only one piece of equipment, a huge polished bowl set in the floor, blazing with reflected light from the single lamp that shone in the ceiling above it.

The Engineer indicated the bowl. "Watch," he told them.

He walked to a board on the opposite wall and swiftly set up an equation on a calculating machine. The machine whirred and clicked and chuckled and the Engineer depressed a series of studs in the control board. The inside of the bowl clouded and seemed to take on motion, like a gigantic whirlpool of flowing nothingness. Faster and faster became the impression of motion.

Gary found himself unable to pull his eyes away from the wonder of the bowl — as if the very motion were hypnotic.

Then the swirl of motion began to take form, misty, tenuous form, as if they were viewing a strange solar system from a vast distance. The solar system faded from view as the vision in the bowl narrowed down to one planet. Other planets flowed out of the picture and the one grew larger and larger, a ball swinging slowly in space.

Then it filled all the bowl and Gary could see seas and cities and mountains and vast deserts. But the mountains were not high, more like weathered hills than mountains, and the seas were shallow. Deserts covered most of the spinning globe and the cities were in ruins.

There was something tantalizingly familiar about that spinning ball, something that struck a chord of memory, something about the solar system — as if he had seen it once before.

And then it struck him like an open hand across his mouth.

"The Earth!" he cried. "That is the Earth!"

"Yes," said the Engineer, "that is your planet, but you see it as it will be many millions of years from now. It is an old, old planet."

"Or as it may never be," whispered Caroline.

"You are right," said the Engineer. "Or as it may never be."

CHAPTER Eleven

TOMMY EVANS" ship rested on one of the lower roofs of the city, just outside the laboratories level. In a few minutes now it would be lifted and hurled through a warp of space and time that should place it upon the Earth they had seen in the swirling bowl… an Earth that was no more than a probability… an Earth that wouldn't exist for millions of years if it ever existed.

"Take good care of that ship," Tommy told Gary. Gary slapped him on the arm.

"I'll bring it back to you," he said.

"Well be waiting for you," Kingsley rumbled.

"Hell," moaned Herb, "I never get to have any fun. Here you and Caroline are going out there to the Earth and I got to stay behind."

"Listen," said Gary savagely, "there's no use in risking all our lives. Caroline's going because she may be the only one who could understand what the old Earth people can tell us, and I'm going because I play a better hand of poker. I beat you all, fair and square."

"I was a sucker," mourned Herb. "I should have known you'd have an ace in the hole. You always got an ace in the hole."

Tommy grinned.

"I got a lousy band," he said. "We should have played more than just one band."

"It was one way of deciding it," said Gary. "We all wanted to go, so we played one hand of poker. We couldn't waste time for more. I won. What more do you want?"

"You always win," Herb complained.

"Just how much chance have you got?" Tommy asked Caroline.

She shrugged.

"It works out on paper," she declared. "When we came here the Engineers had to distort time and space to get us here, but they distorted the two equally. Same amount of distortion for each. But here you have to distort time a whole lot more. Your factors are different. But we have a good chance of getting where we're going?"

"If it's there when you get there…" Herb began, but Kingsley growled at him and he stopped.

Caroline was talking swiftly to Kingsley.

"The Engineer understands the equation for the hyperspheres," she was saying. "Work with him. Try to set up several of them in our own space and see if it isn't possible to set up at least one outside the universe. Pinch it off the time-space warp and shove it out into the inter-space. We may be able to use it later on."

A blast of sound smote them and the solid masonry beneath their feet shivered to the impact of a bomb. For a single second the flashing blaze of atomic fury made the brilliant sunlight seem pale and dim.

"That one was close," said Tommy.

They were used to bombs now.

Gary craned his neck upward and saw the silvery flash of ships far overhead.

"The Engineers can't hold out much longer," Kingsley rumbled. "If we are going to do anything we have to do it pretty soon."

"There is the old space warp again," said Herb. He pointed upward and the others sighted out into space beyond his pointing finger.

There it was… the steady wheel of light, the faint spin of space in motion… they had seen back on Pluto.

The doorway to another world.

"I guess," said Caroline, "that means we have to go." Her voice caught on something that sounded like a sob.

She turned to Kingsley. "If we don't come back," she said, "try the hyperspheres anyhow. Try to absorb the energy in them. You won't have to control it long. Just long enough so the other universe explodes. Then we'll be safe."

She stepped through the air lock and Gary followed her. He turned back and looked at the three of them… great, rumbling Kingsley with his huge head thrust forward, staring through his helmet, with his metal-shod fists opening and closing; dapper, debonair Tommy Evans, the boy who had dreamed of flying to Alpha Centauri and had come to the edge of the universe instead; Herb, the dumpy little photographer who was eating out his heart because he couldn't go. Through eyes suddenly bleared with emotion, Gary waved at them and they waved back. And then he hurried into the ship, slammed down the lever that swung tight the air-lock valves.