Charles Mead stood on top of Hobson’s Hill and stared at the town below, as though trying to imprint a permanent impression of the view on his memory. He paid particular attention to a wood-and-corrugated-iron construction at the bottom of the hill by the railroad tracks, which bore the sign, FINLAY’S LUMBER CO.

Well concealed in the bushes behind him and humming mutely were four black metal boxes forming a small square. Antennae sprouted from each box, curving inward to form an arch in which the light seemed to vibrate and shimmer. Charles Mead made an adjustment on one of the boxes and then stepped quickly into the shimmering arch.

Darkness smothered him immediately. There was a sudden terrifying sensation of weightlessness, of falling. He kept pushing and pushing, although there seemed to be nothing to push against except swirling, spinning blackness.

Then, suddenly, he was standing on another Hobson’s Hill.

The four black boxes had gone, but the blurred arch of light was still there. He fell to his knees, clutching in terror at the grass, trembling and breathless: the switch from one world to another was always unnerving. Immediately between worlds, the sensation of being in no world, of stepping into a bottomless abyss, always left him ragged with panic. He had not made the trip many times before, but he doubted if he would ever get used to it.

The town looked substantially the same as the one he had just left, though he was pleased to note that Finlay’s Lumber Co. was no longer in sight. It was proof that he had made the switch successfully. For some reason, Finlay never seemed to have established his business anywhere but in Charles Mead’s world. There were similar changes in every world--some large changes, some small--but at least Hobson’s Hill was always there, which was why he chose it as his jumping-off point.

Charles Mead set off down the hill and along the highway into town. In a telephone booth, he searched the directory and then began walking again with a new eagerness in his step.

Ten minutes later, he turned onto the front porch of a small, neat brick bungalow. He was about to press the bell button when he paused, listening. From inside the house, he heard voices yelling--a man and a woman--strident with anger.

Charles Mead smiled faintly and rather smugly and put his finger to the button. The voices stopped yelling as the bell jangled somewhere in the house. A moment later, the front door opened and, at the same time, he heard a woman’s high heels stamping through to the back of the house. Then a door slammed.

The man in the doorway wore moccasins, jeans and a red plaid shirt. Except for the general sloppiness of his dress compared with the unwrinkled neatness of Charles Mead’s expensive gray slacks and sports jacket, the pair could have been twins. Both were slim and tall with the slightly stooped appearance of tall men. Their short, sandy hair and wide blue eyes gave them both a boyish look.

“Chuck Mead?” Charles Mead asked. This one was sure to be called Chuck, he thought.

The man nodded, frowning slightly.

“Good,” said Charles. “That’s my name, too. May I come in?”

He pushed his way past the bewildered Chuck Mead, went into the living room and sat down.

He began the speech he had prepared. It was the first time he had said it aloud to anyone and, as he talked, he became painfully aware of how foolish it sounded. He knew that Chuck Mead was smiling behind the hand he so casually cupped over his chin and mouth. In the tiny living room with its fading furnishings, its old mahogany piano and the new TV, its old wedding pictures on the newly redecorated walls, talk of other worlds than this was hopelessly out of place.

“Look, I’m wasting my time trying to explain,” Charles Mead said. “I want you to come with me. Don’t ask questions. What I have to show you will save hours of explanation.”

“What are you going to show me?” Chuck asked.

“Just come with me,” Charles persisted. He knew it was only a matter of time. The bewildering similarity between them had definitely aroused the other’s curiosity. He noticed that although Chuck Mead still smiled, it was an uneasy smile.

“Okay,” Chuck said. “Anything for a laugh. Where do we go?”

“Hobson’s Hill. I suppose you call it that in this world, too?”

“That’s what we call it,” Chuck said, suppressing another grin. “In this world.”

“Let’s go, then,” Charles urged, relieved that the toughest part was over. “There’s nothing to worry about--you’ll be completely safe.”

“Who’s worrying?” challenged his counterpart pugnaciously.

Charles pulled Chuck Mead, fighting and struggling all the way, into his own world and together they stood on Hobson’s Hill, overlooking the town. “Scares me silly every time I make that crossing,” Charles confessed breathlessly.

Chuck’s fingers still clutched his arm, digging painfully into the flesh as though he expected the ground to crumble away at any moment.

“You’re okay now,” Charles reassured him. He pressed the switches on the square of black boxes and the humming noise ceased. The arch collapsed. “Just look around you and see if this isn’t a different world. You’ll notice we have a Finlay’s Lumber Company here, which you don’t have in your world. That’s only one minor difference. Come on home with me and I’ll give you all the proof you could want.”

Charles Mead’s home was a spacious villa set well back from the road in pleasant handsomely kept grounds. They went inside and Charles led the way upstairs to the den, a bright, paneled room at the back of the house.

“Nice place,” Chuck said, awed.

“I suppose it is,” Charles agreed. “Sit down. We’ve got a lot to talk about.”

He poured drinks from a well-stocked cabinet and settled in an easy chair. “Now, then, I want to know if you’re really convinced of this business of other worlds.”

“Sure,” Chuck said, “unless you’ve got me doped or hypnotized or I’m dreaming or something. It all seems real enough.”

“It is real.” Ice cubes clicked as Charles tilted his glass and drank. “Now let’s get down to business. Just listen to what I have to say and don’t interrupt. I want you to think for a moment about those times in your life when you’ve had to make a decision or choose between two alternative courses of action which would affect your whole life. Have you ever wondered, when you’ve made your choice, what would have happened if you had chosen the other alternative? For instance, if you arrived at a situation where two jobs were available and you chose one, wouldn’t you sometimes wonder how things would have been if you had chosen the other job?

“I think I can show you,” he continued, “that when we reach such situations and finally select a course of action, _we also take the other course at the same time_. I’m going to try to prove to you that an alternative world somehow comes into existence in which you live your other life. As a matter of fact, you and I sprang from one of these decisive moments. I’m pretty sure I know which one, too.”

He cut short his guest’s protests with a quick wave of his hand. “You really can’t argue with me about it. You’ve seen two worlds already--surely you don’t think it ends there? After all, we live in an infinite universe; why shouldn’t we be infinite creatures living out the infinite possibilities of our lives? Still, to return to you and me--your wife’s name is Kathy, isn’t it?”

“Yeah. Is yours?”

“My wife is called Estelle. Does that mean anything to you?”

Chuck put down his drink and straightened suddenly. “You mean Estelle Defoe?”

“That’s right. If you want to make sure we’re talking about the same girl, go look out the window.”

Chuck stood up and leaned over the sill. Outside, surrounded by the close-trimmed green lawn, was a swimming pool. Beside the pool, a shapely blonde was stretched out face down on a red towel like some bright, beautiful calendar girl. She wore the bottom half of a green striped bikini; the top half lay on the grass beside her.

“My God! That’s Estelle, all right!” Chuck exclaimed. “I’d know her anywhere. Still got that terrific figure, too!”

“I suppose she is hard to forget after--how long? Just over seven years, isn’t it? Isn’t that how long you’ve been married?”

“How did you know?”

“Can’t you guess? Remember, seven or eight years ago, how you tortured yourself choosing between two girls--Estelle or Kathy? Remember how hard it was arriving at a decision?”

“It wasn’t too difficult. I chose Kathy.”

“I know,” Charles said, smiling. “I was left with Estelle. Or perhaps it was the other way round. Don’t you see: I am you and you are me! If there’s any difference between us, it’s only what the last seven years have done to us. It was one of those decisions I spoke of, when one of us followed one path, leaving the other to explore the other path.”

“That’s crazy! I happen to know Estelle married a major in the Army years ago and went out West to live.”

“In your world, maybe,” Charles said, “but the one in this world married me.”

Chuck looked enviously out of the window. “Lucky you.” He made a gesture that took in the room, the girl, the magnificent house, the beautiful garden. “Did Estelle make you rich, too?”

“Not the way you seem to be figuring. Her father gave me a job in his electronics business and I did some profitable research for him. Now I’m a partner in the firm. We have a big plant on the other side of town. As a matter of fact, it was while I was in the lab out there that I stumbled on these alternate worlds. By sheer accident, I crossed into another world and almost scared myself to death.

“By the way,” he went on, “what happened to you after you married Kathy? I often wondered what it would have been like being married to her.”

“It’s all right, I guess,” Chuck said. “We got married and bought a house. A couple of years ago, I went into business on my own--Hi-Fi and TV repairs. Business isn’t too bad.” He flashed another look at the golden girl sunning herself by the pool. “Estelle hasn’t changed much in all these years,” he said nostalgically. “She’s still as beautiful as ever.”

Then he banged his glass down hard on the window sill. “You must be trying to put something over on me! What’s the gag?”

“There’s no gag,” Charles assured him. “Besides, there’s more to come.”

“Like what?”

“I mentioned earlier about this being an infinite universe. There must be more than just the world you live in and the world I live in. Think it over--millions of everybody making decisions all the time, following one path and discarding another--there must be millions of worlds! An infinite number of them!”

Chuck drained his glass and went back to the cabinet to help himself.