For an instant too long, he thought the scream in the sky was part of the way his head rang after the second detonation of the monster gun. The locomotive had just finished hauling Dora to its next marked firing position. Becker started over to the gun carriage to see if it had stayed level yet again.

The first bomb blast, a few meters behind him, hurled him facefirst into that great mountain of metal. He felt things break-his nose, a cheekbone, several ribs, a hip. He opened his mouth to scream. Another bomb went off, this one even closer.

Jens Larssen’s apartment lay a few blocks west of the Union Stockyards. The neighborhood wasn’t much, but he’d still been surprised at how cheap he got the place. The incessant Chicago wind came from the west that day. A couple of days later, it started blowing off Lake Michigan, and he understood. But it was too late by then-he’d already signed the lease.

The wind blew off the lake the day his wife, Barbara, got into town, too. He still remembered the way her eyes got wide. She put the smell into one raised eyebrow and four words: “Essence of terrified cow.”

The wind was blowing off the lake tonight, but Larssen hardly noticed the rich manure stink. He could smell his own fear, and Barbara’s. Lizard planes were over Chicago again. He’d listened to Edward R. Marrow on crackling shortwave from England, listened to that deep, raspy voice and its trademark opening: “This is London.” Such was Murrow’s magic that he’d imagined he understood what being a Londoner in the Blitz was like. Now he knew better.

More planes screeched past; more bombs fell, some, by the way the windows rattled, quite close by. He clung to Barbara, and she to him, under the kitchen table. Chicago had no shelters. “Hitting the stockyards again,” she said into his ear.

He nodded. “Anything with rails.” The Lizards were inhumanly methodical about pasting transportation hubs, and Chicago was nothing else but. It was also close to the landing zone they’d carved out for themselves in downstate Illinois, Missouri, and Kentucky. Thanks to both those things, the town was taking a heavy pounding.

Only a couple of candles lit the one-bedroom apartment. Their light did not get past the blankets tacked up to serve as blackout curtains. The blankets would not have contained electric lights, but the power had been off more often than it was on the past few days. It made Larssen glad for once that he had only an old-fashioned icebox; not a fancy electric refrigerator. As long as the ice man kept coming around-as long as the ice man still had ice-his food would stay fresh.

Antiaircraft guns, pitifully few and pitifully ineffective, added their barks to the cacophony. Shrapnel pattered down on rooftops like hot metal hail. Air-raid sirens wailed, lost souls in the night.

After a while, Larssen noticed he heard no more Lizard planes, though the rest of the fireworks display continued as gunners blazed away at their imaginations. “I think it’s over,” he said.

“This time,” Barbara answered. He felt her tremble in his arms; for that matter, he felt pretty shaky himself. One by one, sirens fell silent. His wife went on, “I don’t know how much more of this I can handle.” Like a tight-stretched wire, her voice vibrated with hidden stress.

“The English stuck it out,” he said, remembering Murrow again.

“God knows how,” she said. “I don’t.” She squeezed him even tighter than she had when the bombs were falling.

Being a thoroughly rational young man, he opened his mouth to explain to her how bad a beating London had taken, and for how long, and how the Lizards seemed, for the moment anyhow, to be much more selective than the Nazis about hitting civilian targets. But however thoroughly rational he was, the springy firmness of her body locked against his reminded him that he was young. Instead of explaining, he kissed her.

Her mouth came open against his; she moaned a little, deep in her throat, whether from fear or desire or both commingled he never knew. She pressed the warm palm of her hand against his hair. He rolled on top of her, careful even then not to knock his head on the underside of the table. When at last their kiss broke, he whispered, “Shall we go in the bedroom?”

“No,” she said, startling him. Then she giggled. “Let’s do it right here, on the floor. It’ll remind me of those times in the backseat of your old Chevy.”

“All right,” he said, by then too eager to care much where. He shifted his weight. “Raise up, just a little.” When she moved, he undid the buttons on the back of her blouse and unhooked her bra with one hand. He hadn’t tried that since they were married, but the ease with which he accomplished it said his hand remembered the backseat of the old Chevy, too.

He tossed the cotton blouse and bra aside. Presently, he said, “Lift up again.” He slowly slid her panties down her legs. Instead of pulling off her skirt, he hiked it up. That made her laugh again. She kissed him, long and slow. His hands wandered where they would.

So did hers, unbuckling his belt, opening his trouser button, and, with several delicious pauses, lowering his zipper. He yanked down his pants and jockey shorts, just far enough. They were both laughing by then. Laughing still, he plunged into her, leaving behind for a little while the terror outside the blacked-out apartment.

“I should have taken off my shirt,” he said when they were through. “Now it’s all sweaty.”

“It? What about me?” Barbara brought both hands up to his chest, made as if to push him vertically away from her. He raised up on his elbows and knees-and this time did catch the back of his head on the bottom of the kitchen table, hard enough to see stars. He swore, first in English, then in the fragments of Norwegian he’d picked up from his grandfather.

Barbara, whose maiden name was Baker and who had a couple of several-times-great-grandfathers who’d fought in the Revolution, always thought that was the funniest thing in the world. “You’re in no position to laugh now, wench,” he said, and tickled her conveniently bare ribs. The linoleum made moist squelching noises under her backside as she tried to wriggle away. That set him laughing, too. He grabbed her. They might have begun again, but the telephone chose that moment to ring.

Larssen jerked up in surprise-he hadn’t thought the phone was working-and, gave himself another crack in the head. This time he started out swearing in Norwegian. Trousers flopping around his ankles, he hobbled into the bedroom. “Hello?” he growled, annoyed as if it were the caller’s fault he’d knocked his brains loose.

“That is you, Jens? You are all right, you and Barbara?”

The accented voice on the other end of the line threw ice water on his steam. “Yes, Dr. Fermi,” he said, and made a hasty grab for his pants. Of course Fermi could not see him, but he was embarrassed even to be talking to the Italian physicist, a dignified man if ever there was one, with trousers at half-mast. “We came through safe again, thank you.”

“Safe?” Fermi echoed bitterly. “This is a word without meaning in the world today. I thought it had one when Laura and I came here four years ago, but I am wrong. But never mind that. Here is the reason I call: Szilard says-and he, is right-we must all meet tomorrow, and tomorrow early. Seven o’clock. He would say six if he could.”

“I’ll be there,” Larssen promised. “What’s up?”

“The Lizards, they are moving toward Chicago.”

The words seemed to hang on the wire. “But they can’t,” Jens said, though he knew perfectly well they could. What the devil was there to stop them?

Fermi understood what be meant. “You are right-they must not. If they come here, everything we do since we begin is lost. Too much time lost, time we have not to waste even against Germany, to say nothing of these creatures.”

“Germany.” Larssen kept his voice flat. He’d been relieved past all measure when the atomic bomb that exploded above Chicago proved not to have a swastika painted on its casing. He once more had no idea how far along the Nazis were on their own bomb program. It would be a hell of a note, though, for humanity to have to depend on them alone for a weapon with which to do the Lizards some real damage. He wondered if he would sooner see Earth conquered than Adolf Hitler its savior. Just maybe, he thought. On the line, Fermi cleared his throat. That brought Larssen back to the here-and-now. “I’ll be there,” he said again.