Half of Jupiter’s great disk and most of the other moons were below the horizon when the man stepped out of the plane and changed her life. As far as Carol Marsh was concerned, he was ordinary enough in appearance. And she wasn’t ordinarily attracted to ordinary men.

He was slightly over medium height, his features were not quite regular, and he had a deep tan over what had started out as a sunburn, so that she decided he had misjudged the strength of the sun on some planet with a thin atmosphere.

She frowned as she watched him look around. She was annoyed by the fact that it took him almost a minute to get his bearings and realize that she was first, a human being and second, a girl well worth a man’s attention.

Even the troubled expression in his eyes was something she held against him. A man shouldn’t look troubled. A man should be confident, self-assured in a manner that also assured the girl he spoke to. She remembered that back on Earth John Burr had been completely self-assured.

It was startling to realize that it was with this newcomer, whose appearance she had every reason to dislike, that she had fallen suddenly and completely in love, as suddenly and completely as if she had fallen off a cliff.

“I’m looking for some people,” he said. “But I suppose--” His very voice was ill at ease, and that was something else she should have held against him. And against herself. She had always resented men whose voices betrayed their lack of confidence. “I suppose it’s no use,” he went on. “I’d recognize the house.”

“Who are the people you’re looking for?”

He took out a wallet, and from it drew a stereo picture. Two children, a boy and a girl, were standing with a smiling young woman in front of a sturdy, old-fashioned plastic house. Their clothes were out of fashion by a year or so, but that depended on where you were. Mars, for instance, was always three years behind Earth. Here on Ganymede, on the other hand, you might even be ahead of Earth in some respects.

As Carol’s eyes lifted to his, she saw him staring at the picture with such longing that she at once knew herself for a fool. They’re his wife and children, she thought. He’s trying to find them. And I had to fall in love with him at first sight.

His eyes were on her now, and she said, “I’m sorry, I’ve never seen them.”

“Have you lived around here long?”

“Five years.”

“Then this can’t be the place.” He stood there irresolutely and started to turn slowly away without even a word of thanks to her.

“My father may have heard about them,” said Carol, knowing herself for a fool again.

Past experience, she told herself ruefully, had taught her nothing. The thing to do was to let him go and forget him as quickly as possible, before she learned anything about him, before her feeling for him could become anything more than an irrational, momentary impulse. The stronger the bonds of knowledge and interest between them, the more painful they would be to break. And the breaking was inevitable.

The house where she and her father lived was a simple dome-shaped building, its walls and furniture both made of a silicon plastic whose raw materials had come from the ground on which it stood. There were rugs and draperies of a slightly different composition, woven on the all-purpose Household Helper that her father had bought before leaving Earth. They lived comfortably enough, she thought, as she led the man in.

But he hardly noticed the house or anything in it. When they reached the library and her father looked up from the book he was reading, only then did the man display interest. The book was a favorite of her father’s and it made him unhappy to cut his reading short.

Nevertheless, he turned off the projector, stood up, and said, “Yes, Carol?”

“This man is looking for some--some friends of his, Dad. I thought you might be able to help him.”

She held out the picture and, to her relief, her father stared at that instead of at her. Sometimes he was a little too shrewd; if she was making a fool of herself, there was no need for him to know it. He could be a sardonic man and he did not suffer fools gladly, even in his own family. He was of the opinion that she had used up her quota of foolishness with John Burr.

He was shaking his head. “Sorry, I’ve never seen them. Are you sure they live around here?”

“No,” said the man. “I’m not sure. I’m not sure of anything, except that they’re my wife and kids. And I’ve got to find them.”

“Have you checked at the District Office?”

“I did that first. They couldn’t help me, but they said their records weren’t complete yet.”

“They’re complete enough, I should think. Maybe they don’t list every prospector who wanders around without settling down, but they wouldn’t be likely to miss a woman and two children. I’m afraid that you’re wasting your time looking on Ganymede.”

The man’s face clouded. “It isn’t a waste of my time,” he said. “I’ve got nothing else to do with it. And I have to find them. They need me.”

Mr. Marsh looked away from the man to his daughter, and Carol was a little slow in avoiding his eyes. “I see,” he said, and she had an idea of what he meant by that. He saw too much.

If he knew, there was nothing she could do about it. She said, “Perhaps Mr.--”

She paused, and the man said dully, “Callendar.”

“Perhaps if Mr. Callendar would have dinner with us and tell us a little more, we’d be better able to help.”

“Not a bad idea, Carol. We should know a little more.”

Carol selected a dinner and pressed the button that would start its preparation.

Her father said casually, “You are a stranger to Ganymede, aren’t you, Mr. Callendar?”

“I’m not sure of that,” said the man.

Her father’s eyebrows went up.

Carol said, “But you do come from one of Jupiter’s moons?”

“I can’t remember which one. There are a lot of things that my memory’s hazy about. I can’t even recall the name of the company I worked for as an engineer.”

“That may not be so strange. I find difficulty remembering the school where I taught on Earth. P.S. 654, wasn’t it, Dad?”

“P.S. 634,” Mr. Marsh corrected briefly.

“You see?” she said. “Do you remember your wife’s name? And the names of your children?”

“I wouldn’t forget them,” he said. “My wife’s name was Mona.” He stared at the wall for a moment, his face without expression. “I can still see the way she looked when I left to undergo treatment. Paul was--let’s see, he must be about nine, maybe ten, by this time. And Wilma must be six or seven. I remember how scared she was that time she found a harmless little phytopod. She thought it was going to bite her.”

“Phytopod?” said Carol. “We don’t have them around here. What do they look like?”

“They’re small and furry, and have two feet that look like roots. When they stand still you’re likely to mistake them for plants.”

“You do recall some things,” said Carol.

“The little things that don’t tell me where to look. I remember the time we went on a picnic--I don’t recall how many moons there were in the sky--and the ground began to shake. It didn’t do any damage, but Wilma was terrified. Paul took it in his stride, though.”

“There aren’t any earthquakes on Ganymede,” said her father. “If your memory of that incident is correct, you’re looking in the wrong place.”