Joe groaned. "A little knowledge is a gruesome thing." 

There was a stir across the room as Oppy and Kitty arrived. Better than a stir, veneration. The Director of the Los Alamos project was a spindly six feet tall with a close-cropped skull and beak of a nose that emphasized tapered eyes of startling blue. Younger physicists followed him, copying the hunch of his shoulders, his air of distraction. Kitty Oppenheimer had a flat, pretty face, a frowsy dress and dark, thick hair. Her friends were European wives, who surrounded her like bodyguards. A fingertip slid down Joe's spine. There were people at the end of the piano, but they were watching dancers or the Oppenheimers. Harvey was concentrating on his clarinet. The fingertip turned to fingernail. Joe glanced up at Mrs Augustino, the captain's wife She looked like a cover of Life magazine, maybe "Life goes to Magnolia Country" with her peroxide-blonde curls, blue eyes and polka-dot dress with ruffled shoulders, and she seemed to be intently watching the couples on the floor, but it was her finger, nonetheless.

"What is this secret project, Sergeant?" she asked in a voice soft enough for just him to hear. "What do you think they're making?"

"Why don't you ask your husband?"

"Captain Augustino took me to a nightclub in Albuquerque last week." Her nail continued like a little knife down the groove of his back. "You were playing. I was struck by how gently you played. Is that because your fingers are so big?"

"Not gently. Carefully. I stay out of trouble." By twisting on the bench to look at her, he managed to dislodge her nail. Sad: nineteen, twenty years old and already a bored Army wife. "What do you think they're doing here, Mrs Augustino? What's your opinion?"

She brushed curls from her face and surveyed the room. "I think the whole thing is a hoax. They're dodging the draft. All these so-called scientists got together and pulled the wool over the Army's eyes. They're smart enough to do it."

"Yeah," he had to agree, "they are."

During the break, Joe had to manoeuvre around some of the "so-called scientists" to get to the bar. The Hungarian, Teller, his eyebrows rising like fans, brayed over a joke by Fermi. A short man, Fermi was fit and balding and wore a rough double-breasted suit and thick-soled shoes that curled at the toe like an Italian peasant's. Physicists called him "the Pope".

Oppy was showing a circle of admirers how to build the perfect martini.

"Firm instructions should always be in German." He had the trick of lowering his voice so listeners leaned forward, and as they did so he poured gin to the brim of the glass. "Am wichtigsten, der Gin sollte gekühlt sein, kein Els." "Bourbon," Joe told Foote, who, drunk or not, was tending bar.

"Zwei Tropfeln Wermut, nicht mehr, nicht weniger, und eine Olive." Oppy added enough vermouth to cause an oily swirl in the gin, then he handed his concoction to a woman with red-orange hair. She would have been noticeable simply because she wore black coveralls that suggested she was a member of an army of Amazons, or laboured in a factory of mourners, or had been dipped in ink. It was the sheer intellectual cast of her face that really set her apart. Black hair cut in severe bangs around eyes that were blue-gray with dark edges that dilated with dislike, like a cat's. Strong nose, full mouth and the sort of pale complexion that scorned the sun. She was exactly the sort of female that attracted Oppy and repelled Joe. "A double," Joe told Foote.

Oppy said, "Joe, meet Dr Anna Weiss. Anna, this is my oldest friend here, Joe Pena."

Drinks in hand, Anna Weiss and Joe dismissed each other with a nod.

"I missed my first year at Harvard," Oppy persisted. "My family sent me to New Mexico for my health. They contracted with Joe's father, a renowned bootlegger."

"That so?" She had a low voice and a German accent and no interest.

"Tell her, Joe," Oppy said.

"My dad also rented packhorses and experienced guides for dude parties," Joe said. "I was the experienced guide. I was twelve. One of the first times I went out, I had a kid from New York. Sixteen and so tall and skinny that the first time I saw him in swimming trunks I thought he was going to die on the trail."

"I couldn't ride," Oppy said.

"He couldn't ride to save his life," Joe said, "but he liked to go out at night to see stars. He was so damned night blind I had to hold back every branch on the way. One night we got caught in a rainstorm and I got under my horse to stay dry. I heard this guy yelling in the rain."

"I thought he'd left me," Oppy said.

"I told him to come down under the horse with me. He came down, soaked, got under the horse and said, 'Gee!' Because he'd never thought of the possibility of getting under a horse in the rain. That loomed like a brilliant idea to him."

"It struck me as an offer of eternal friendship," Oppy said. "At the end of the rain he led me up to the Ranch School here, to this very place, for some coffee and dry clothes. That was twenty years ago."

Her eyes moved from man to man as if they were describing a previous life as idiots.

"Better switch back to German," Joe told Oppy and took his drink out to the patio. There was a low moon over the mountains and a liquid coolness to the air. By the flagstones was a garden that was deep in the shadow of poplars. "Los Alamos" meant "The Poplars".

What are they doing here? An atomic bomb, a nuclear device, whatever those words signified. He couldn't help but know the terminology from being Oppy's driver and overhearing conversations in the back seat. As for understanding, it was all a different language to Joe. Chain reaction? Fast neutrons and slow neutrons? Incomprehensible, like Sanskrit. Of course, Oppy read Sanskrit.

Joe set his drink on a flagstone and lit his first Lucky of the day. He still had the habits of a fighter trying to stay in shape, although for what he didn't know.

As Teller came through the doors, he said: "Joe, you could take lessons and become a real pianist. You could play Beethoven."

"Ah, the big-band sound," Joe said. As soon as he could he picked up his drink and slipped away from an analysis of the American jitterbug. Teller had a wooden leg.

Joe was nearly at the doors when his way was blocked by Anna Weiss, the woman Oppy had been instructing in the manufacture of martinis. With her was another emigre. He had a bland and pasty face, straw-coloured hair and rimless glasses. His name was Klaus Fuchs. Joe couldn't remember passing a single word with him. Apparently Fuchs has been giving Fraulein Weiss the usual Los Alamos tour: there are the mountains, there are the mesas, there is the Indian.

"So, you were the one who first brought Oppy here?" she said to Joe.

He nodded. "This was a private school then. A year at the Ranch School cost more than Harvard. The war wiped it out."

"And led you back. That is irony?"

"No, that's pure Army."

The two Germans seemed to stare at Joe from the far end of a scale of intelligence.

"Teller is telling everyone you are musical," she said. "Klaus says you have no actual ability."

Fuchs shrugged. "It should be enough to be a war hero."

"You're kind," Joe said. "Of course, it's important to be on the right side of the war."

"They grow up with rifles here, Dr Fuchs," a voice said from the dark of the garden. "It's a simple thing to be a war hero if you can fire a rifle."

"I have never shot anything," Fuchs said.

"Of course not." Captain Augustino took a step towards the patio, just enough for them to see him. "In fact, we're in hunting season now. I wouldn't go wandering in the woods."

"Naturally," Fuchs said.

"A moon like this, maybe snow, every Indian is going to be out for his deer tonight. It could be dangerous."