"It means," the lieutenant said, as if he were answering a question she hadn't yet asked, "that the Earth we are returning to is not the Earth we left." "I don't understand," she gasped. "There's a theory," Lt. Harper answered slowly. "Heretofore it has been considered only a mathematical abstraction, and having no counterpart in reality. The theory of multiple dimensions." She looked at him closely, and in her habitual ambivalence of thought reflected that he sounded much more intelligent than she had suspected. "I've read about that," she answered. He looked relieved, and threw a quick look at Sam. Apparently he had underestimated her intelligence, too--in spite of all her degrees. * * * * * "We never thought it could be real," he emphasized. "But the theory was that multiple universes lay side by side, perhaps each an instant's time away from the other. The only thing I can see is that some flaw in the space warper threw us out of our dimension into another one closely adjacent--not far enough for things to be totally different, just different enough that the duplication isn't identical. It's Earth, but it's not our Earth. It's a New Earth, one we don't know anything about." "In another few hours, we'll be entering the atmosphere," Sam put in, "and we don't know what we'll find. We thought you ought to know." She flared in exasperation at the simple assumption of male arrogance. "Of course I should know!" she snapped back. "I am not one of your little bits of blonde, empty-headed fluff to be protected by strong males! I should have been told immediately!" Lt. Harper looked at Sam with a broad grin. It was amusement, but it was more--a confirmation that they could depend on her to take it in her stride--an approval. Apparently, they had discussed more things about her than she'd overheard, while she slept. He didn't turn off the grin when he looked directly at her. "What could you have done about it, if we had told you, Miss Kitty?" he asked mildly. * * * * * It was not the same Earth. The charts and maps had not been wrong. Her tentative theory that perhaps there were vision flaws in the plastic nose window which had not stood up. The continents, the lakes, the rivers--the topography really was distorted. Now there was the Mississippi River, one spot swinging rather too widely to the East. The Great Lakes were one huge inland sea. The Gulf of Mexico swung high up into what had once been Alabama and Georgia. There was no New Orleans, shipping center of the world, headquarters of Space.