After the soldiers and the wagons passed, the Westsiders started drifting back toward their homes. “Show's over,” Liz 's mother said. '“Now we hope we don't seen the soldiers for a while, 'cause if we do-”

“Something's gone wrong somewhere,” Dad finished for her.

“Well, yes.” Mom sent Dad a dirty look. Liz didn't blame her. She didn't like getting her lines stepped on, either.

The dirty look sailed over Dad's head the way a badly aimed arrow would have. He said, “Let's get back to the house.”

Getting back to the house, of course, meant walking back to the house. That was a couple of miles- Liz more readily thought of it as three kilometers-and took more than half an hour. Going from one place to another here was like traveling in the home timeline in one way. Ten minutes of travel was a short trip, half an hour was kind of medium, an hour was long, and two hours was a pain in the neck reserved for something that had better be special.

But how far you went in your time shrank drastically. Here you traveled on foot, or maybe on horseback. If you were very rich, you might have a carriage. Some bicycles survived, but their rubber tires didn't. With wooden tires, riding them was a good way to shake your kidneys loose.

And so you mostly didn't go more than four or five miles- six or eight kilometers-from where you lived. As they had in the days before trains and cars and planes, people lived their whole lives within twenty or thirty miles of where they were born. If this alternate didn't regain its technology, lots of little, very different peoples would sprout from the ruined tree trunk of the USA.

That was already starting to happen. The Westside and the Valley weren't just independent countries. People in both of them spoke English, but it wasn't quite the same English. People from the Valley had a nasal accent that made it pretty easy to pick them out from Westsiders by ear. In another few hundred years, the two dialects might turn into separate languages. Even if they didn't, it was pretty clear that people from Southern California would have trouble understanding people from the upper Midwest. And both those groups would have trouble with the language they spoke in the deep South.

Liz looked around to make sure no locals could overhear. When she saw they couldn't, she asked, “Is what I'm getting out of the library helping you figure out just where this alternate split off from the home timeline?”

“It will help. It's bound to,” her mother answered.

“It may take a while, though,” her father added. “I envy ancient historians. There's only so much for them to know. It's not like that when you get up into the twentieth century. You're drowning in data. It does seem plain that the breakpoint has to do with the Vietnam War, though.”

“We already knew that,” Liz said. “Or we were pretty sure, anyhow.”

Her father nodded. “It was always a good bet, since the big war started while the Vietnam War was going strong. But it still isn't obvious whether the U.S. escalation here scared the Russians enough to make them start throwing rockets, or whether the United States threw them first when we didn't like what Russia and China were doing.”

“Whoever shot first, an awful lot of people on both sides ended up dead.” Liz eyed this sorry version of the UCLA campus. “And there's been nothing but trouble ever since.”

“Nobody's going to tell you you're wrong, hon,” her father said. “At that, they got off lucky here. They got bombed back to the Middle Ages, but they didn't get bombed back to the Stone Age.”

“They didn't all get killed, either,” Mom said. “That happened in some alternates.”

Liz nodded. People really could be stupid. Just in case the home timeline didn't have enough examples of that, the alternates offered even more. People in the home timeline hadn't been stupid some ways. They hadn't tried blowing one another off the map with H-bombs, for instance. They were proud of that, and relieved about it, too.

Seeing what other people, people much too much like them, had done in different alternates should have made them prouder of escaping-and also more relieved. To some degree, it did. But only to some degree. Too many people in the home timeline still had axes to grind. Big wars seemed unlikely these days. Terrorist strikes, on the other hand…

“I've got a question,” Liz said.

“What?” her mother and father asked together.

“What happens if something now makes the home timeline split into two alternates?” Liz said. “They'd both have Crosstime Traffic in them. Which one would be the real home timeline?”

Mom and Dad looked at each other. They walked on for several steps without answering. At last, her father said, “If there are no other questions, class is dismissed.”

“Dad!” Liz said reproachfully.

“We're just historians. We can't deal with questions like that,” her mother said. “You need to talk to the chronophysicists. If anybody can tell you, they're the ones.”

“Talk to them at a convention, after they've got a few drinks under their belts,” Dad added. “If you get 'em when they're in the lab, they'll look wise and tell you things like that can't happen. I hope they're right. Everybody does.”

“How will we find out?” Liz asked.

“The same way people usually do, I bet,” her father answered. “The hard way.”

“Come on! Come on! Get moving!” Sergeant Chuck booted Dan in the seat of the pants. He didn't kick him hard enough to hurt, but it was plenty hard enough to wake him.

Chuck went on shouting and booting other soldiers awake. Dan yawned and stretched and looked around. The sun hadn't risen yet, but it would soon. It was already bright enough to see colors. Only a handful of the brightest stars still shone, and they faded out as he watched.

He pulled a square of hardtack and some smoked sausage from his pack. Some soldiers crumbled up their hardtack and fried it in bacon grease. He just crunched on his. You needed good teeth to do that. He had good teeth, and knew how lucky he was to have them. Wounded soldiers got ether before surgeons went to work on them. Ordinary people with toothaches? You needed to be rich to get knocked out before a dentist pulled a tooth that was driving you nuts.

“Everybody ready?” Captain Kevin called. “You better be ready, 'cause we're moving out!”

Dan stuffed a last chunk of sausage into his mouth. As he chewed on it, he probably looked like a hamster with its cheek pouches full. He didn't care. He kind of liked hamsters. They were a lot cuter than rats and mice. They didn't have pointy noses, and they didn't have long, naked tails, either.

Old men and women said their grandparents said there hadn't been any wild hamsters before the Fire fell. There also hadn’t been any wild iguanas or parrots. And lakes and ponds hadn't had any piranhas in them. Dan wasn't sure he believed that. Wasn't it like saying there'd been a time without possums and starlings and cabbage butterflies? If there had been a time like that, nobody remembered it now.

“Form up!'“ the captain shouted. “Chances are we'll be in action later on today.”

The soldiers who were about Dan 's age hurried into place. They were as eager as he was. Older men, men who'd gone to war before, didn't move so fast. Dan thought that was because they were old. That it might be because they'd already seen battle and didn't much care for it never crossed his mind.

As carefully as if handling gold and precious jewels, the machine-gun crew loaded their lovely weapon onto the pack horse's back. Extra ammunition went onto another horse. When the men waved to Kevin, he got the company moving.

“Be alert-the enemy may have pushed scouts forward,” he warned.

That made Dan try to look every which way at once. Old Sepulveda gave scouts plenty of places to hide. One could lurk in any of those dead houses, watching the Valley soldiers with field glasses. But if one was, how would he get word back to his commanders? This wasn't the Old Time. He wouldn't have a television or a radio or a telephone handy.