"I think so. I can't really be sure."

They paused on the low ledge where he had stood earlier and watched the girls gather their data for the reports. At their feet the waves washed up to the edges of the tide pools, eddying into and out of them softly. The water looked dark and cold, but they knew that it too was warm.

"There've been lots of changes, and they all fit a pattern," he said.

"The temperature. The difference in salt content in the water. The higher tides. Those things could happen for several reasons. But there's only one explanation for the other changes, the ones I found on the star charts."

She waited. The water lapped in and out, reaching almost to where they stood.

"The Earth rotates faster now," he said. "And the stars are nearer.

Much nearer than they were."

"Isn't that impossible?"

"How do we know? We exceeded the speed of light. Who could say what continuum that might have put us in? I remember an a.n.a.logy I read once, in a layman's book on different theories of s.p.a.ce-time. '--The future and the past, two branches of a hyperbola, each with the speed of light as its limit--'"

"You mean," she whispered, "that we're not in the future at all? We're in the past--the far past--before there was any life on Earth?"

He looked down at the pools of water at their feet, the lifeless water that according to all their old discarded theories should have been teeming with life. He nodded slowly and lifted the gla.s.s cylinder he had brought from the ship and stared at it.

"That bottle," she whispered. "You filled it with bacteria, didn't you?"

He nodded again.

"You're mad, Hugh. You can't mean that _that bottle_ is the origin of life on Earth! You can't."

"Maybe this isn't our Earth, Nora. Maybe there are thousands of continuums and thousands of Earths, all waiting for a ship to land someday and give them life."

Slowly he unstoppered the cylinder and knelt down at the water's edge.

For a minute he paused, wondering if there were other continuums or only this one, wondering just how deep the paradox lay. Then he tipped the bottle up and poured, and the liquid from the cylinder ran down into the tide pools and eddied there and was lost in the liquid of the ocean. He poured until the bottle was empty and all the single-celled bacteria from the ship's tank mingled with the warm, lifeless waters.

The water temperatures were the same. Everything was the same, and the conditions were very favorable and the bacteria would divide and redivide and keep on dividing for millions of years.

"We'll hold the ship under light speed," he said. "And in a few million years we can drop back here and see how evolution is getting along."

He stood up and she took his hand and moved closer to him. They were both shivering, despite the warmth of the air.

"But how did life originate in the beginning?" she asked suddenly.

Hugh McCann shook his head in the darkness. "I don't know. We've been all over the galaxy and haven't found life anywhere. Perhaps it can't have a natural cause. Perhaps it's always planted. A closed circle from beginning to end."

"But something--someone--must have started the circle. Who?"

He looked down at the empty cylinder that he had dropped at the water's edge and then he looked out at the ocean, lifeless no longer.

And once again he shook his head.

"We did, Nora. We're the beginning."

For a long moment their eyes met and held, and then they turned and walked away from the ocean, back toward the ship, and the people. And the moonlight glinted off the empty bottle.

THE END