"You think it might tip us back?"

"Maybe. I don't know. It's a gamble. It might tip you back to your own time, or it might not. If not -"

"If not we wouldn't have a chance of survival."

Douglas flicked out a pocket map and spread it open on the couch. "A patrol will remain in this area another half-hour. If you decide to come undersurface with us, go down the street this way." He traced a line on the map. "To this open field here. The patrol is a Political unit. They'll take you the rest of the way down. You think you can find the field?"

"I think so," Tim said, looking at the map. His lips twisted. "That open field used to be the grammar school my kids went to. That's where they were going when the troops stopped them. Just a little while ago."

"Seven years ago," Douglas corrected. He snapped the map shut and restored it to his pocket. He pulled his mask down and moved out the front door onto the porch. "Maybe I'll see you again. Maybe not. It's your decision. You'll have to decide one way or the other. In any case – good luck."

He turned and walked briskly from the house.

"Dad," Earl shouted, "are you going in the Army? Are you going to wear a mask and shoot one of those guns?" His eyes sparkled with excitement. "Are you going to drive a snake?"

Tim McLean squatted down and pulled his son to him. "You want that? You want to stay here? If I'm going to wear a mask and shoot one of those guns we can't go back."

Earl looked doubtful. "Couldn't we go back later?"

Tim shook his head. "Afraid not. We've got to decide now, whether we're going back or not."

"You heard Mr Douglas," Virginia said disgustedly. "The attack's going to start in a couple hours."

Tim got to his feet and paced back and forth. "If we stay in the house we'll get blown to bits. Let's face it. There's only a faint chance we'll be tipped back to our own time. A slim possibility – a long shot. Do we want to stay here with roms falling all around us, knowing any second it may be the end – hearing them come closer, hitting nearer – lying on the floor, waiting, listening -"

"Do you really want to go back?" Mary demanded.

"Of course, but the risk -"

"I'm not asking you about the risk. I'm asking you if you really want to go back. Maybe you want to stay here. Maybe Earl's right. You in a uniform and a mask, with one of those needle guns. Driving a snake."

"With you in a factory-labor camp! And the kids in a Government Relocation Center! How do you think that would be? What do you think they'd teach them? What do you think they'd grow up like? And believe…"

"They'd probably teach them to be very useful."

"Useful! To what? To themselves? To mankind? Or to the war effort…?"

"They'd be alive," Mary said. "They'd be safe. This way, if we stay in the house, wait for the attack to come -"

"Sure," Tim grated. "They would be alive. Probably quite healthy. Well fed. Well clothed and cared for." He looked down at his children, his face hard. "They'd stay alive, all right. They'd live to grow up and become adults. But what kind of adults? You heard what he said! Book burnings in '77. What'll they be taught from? What kind of ideas are left, since '77? What kind of beliefs can they get from a Government Relocation Center? What kind of values will they have?"

"There's the id block," Mary suggested.

"Industrial Designing and Technology. For the bright ones. The clever ones with imagination. Busy slide rules and pencils. Drawing and planning and making discoveries. The girls could go into that. They could design the guns. Earl could go into the Political Service. He could make sure the guns were used. If any of the troops deviated, didn't want to shoot, Earl could report them and have them hauled off for reeducation. To have their political faith strengthened – in a world where those with brains design weapons and those without brains fire them."

"But they'd be alive," Mary repeated.

"You've got a strange idea of what being alive is! You call that alive? Maybe it is." Tim shook his head wearily. "Maybe you're right. Maybe we should go undersurface with Douglas. Stay in this world. Stay alive."

"I didn't say that," Mary said softly. "Tim, I had to find out if you really understood why it's worth it. Worth staying in the house, taking the chance we won't be tipped back."

"Then you want to take the chance?"

"Of course! We have to. We can't turn our children over to them – to the Relocation Center. To be taught how to hate and kill and destroy." Mary smiled up wanly. "Anyhow, they've always gone to the Jefferson School. And here, in this world, it's only an open field."

"Are we going back?" Judy piped. She caught hold of Tim's sleeve imploringly. "Are we going back now?"

Tim disengaged her arm. "Very soon, honey."

Mary opened the supply cupboards and rooted in them. "Everything's here. What did they take?"

"The case of canned peas. Everything we had in the refrigerator. And they smashed the front door."

"I'll bet we're beating them!" Earl shouted. He ran to the window and peered out. The sight of the rolling ash disappointed him. "I can't see anything! Just the fog!" He turned questioningly to Tim. "Is it always like this, here?"

"Yes," Tim answered.

Earl's face fell. "Just fog? Nothing else. Doesn't the sun shine ever?"

"I'll fix some coffee," Mary said.

"Good." Tim went into the bathroom and examined himself in the mirror. His mouth was cut, caked with dried blood. His head ached. He felt sick at his stomach.

"It doesn't seem possible," Mary said, as they sat down at the kitchen table.

Tim sipped his coffee. "No. It doesn't." Where he sat he could see out the window. The clouds of ash. The dim, jagged outline of ruined buildings.

"Is the man coming back?" Judy piped. "He was all thin and funny-looking. He isn't coming back, is he?"

Tim looked at his watch. It read ten o'clock. He reset it, moving the hands to four-fifteen. "Douglas said it would begin at nightfall. That won't be long."

"Then we're really staying in the house," Mary said.

"That's right."

"Even though there's only a little chance?"

"Even though there's only a little chance we'll get back. Are you glad?"

"I'm glad," Mary said, her eyes bright. "It's worth it, Tim. You know it is. Anything's worth it, any chance. To get back. And something else. We'll all be here together… We can't be – broken up. Separated."

Tim poured himself more coffee. "We might as well make ourselves comfortable. We have maybe three hours to wait. We might as well try to enjoy them."

At six-thirty the first rom fell. They felt the shock, a deep rolling wave of force that lapped over the house.

Judy came running in from the dining-room, face white with fear. "Daddy! What is it?"

"Nothing. Don't worry."

"Come on back," Virginia called impatiently. "It's your turn." They were playing Monopoly.

Earl leaped to his feet. "I want to see." He ran excitedly to the window. "I can see where it hit!"

Tim lifted the shade and looked out. Far off, in the distance, a white glare burned fitfully. A towering column of luminous smoke rose from it.

A second shudder vibrated through the house. A dish crashed from the shelf, into the sink.

It was almost dark outside. Except for the two spots of white Tim could make out nothing. The clouds of ash were lost in the gloom. The ash and the ragged remains of buildings.

"That was closer," Mary said.

A third rom fell. In the living-room windows burst, showering glass across the rug.

"We better get back," Tim said.

"Where?"

"Down in the basement. Come on." Tim unlocked the basement door and they trooped nervously downstairs.

"Food," Mary said. "We better bring the food that's left."