Joe pushed open Ray's door. Ray leaned woodenly to one side so Santa could slip through to a fold-down seat. Already the lead sedan and truck, then ambulance and tail sedan were turning round the petrol pumps for the remaining 450 miles to New Mexico and the Hill.

"Nose wipes, boys." Santa handed up cotton swabs. "All part of the routine."

Joe and Ray stuck the swabs up their noses, then handed them back to Santa who dropped them into separate envelopes.

"It isn't routine for us to make this run," Joe said. "It isn't routine for you to be on it."

"We're bodyguards," Ray said through his teeth. "We're not guinea pigs. They got enough crazy truckers for this run."

"Why do you think they chose you, Sergeant Stingo?" Santa hunched over Ray's shoulder.

"Because they hate me."

"If they hated you they wouldn't have asked me to bring the nose wipes. That's to help check any respiratory radioactivity. When we arrive, they'll take a blood sample and perhaps burn your clothes. Would they take those precautions if they didn't care about you?"

"True," Ray relented.

"You just need a ride from Salt Lake City?" Joe asked as Santa moved to his shoulder. "Why are you here?"

"I'll tell you why they hate me," Ray interrupted. The amphetamines fuelled his paranoia and turned the whites of his eyes pink. "For the first time in my life I'm ahead of the game. My father runs a garbage truck, my three brothers run garbage trucks, and they make $50 a week. I got $10,000 in poker money. I'm getting out of this fucking war with both legs and both arms. When I go back to Jersey I can buy a liquor store. I'll get my own fighters, maybe I'll manage. Get a boat at the shore, get married, have kids. They don't want me to have that."

"Why didn't you mention your mother?" Santa moved back to Ray's shoulder.

"What about my mother?" Ray whipped round. Because he still held the Tommy gun, its barrel pointed at Santa.

"Don't ask a man about his mother," Joe told Santa and pushed the barrel up.

"Why do you think Sergeant Stingo is nervous?"

"Because the Army hates enlisted men, which you are not."

"So why are you here?" Ray asked.

Santa smiled patiently. Fine skin crinkled around his pale blue eyes. His nose and cheeks had the rosy hue of a lifetime of long walks and of the San Francisco Bay and the mellow sun. His Harris tweed jacket smelled like a potpourri of pipe tobacco and bay rum. His hair sprung in white spirals, thin on top, thick at the sides, wisps from the ears. Everyone on the Hill had naturally nicknamed him "Santa". Everyone but Harvey. Harvey called him "Bugs Bonney".

"I'm deeply enthused about the time we're going to be sharing," Santa said. "I understand we'll be driving through some spectacular scenery. In fact, in the garage I heard one of the officers refer to these shipments of -" Santa cleared his throat to indicate the plutonium hanging in the canister behind him - "as the Razzle-Dazzle Express."

"See any officers in here?" Ray muttered. "It's the fucking, glow-in-the-dark Asshole Express."

The Mormon temple swung to the north and shrank to the size of a claim stake under the immense Utah afternoon. The mountains started huge and grew. As the convoy gathered speed through the wide Jordan Valley, Ray looked as though he were entering a black tunnel.

The square and straps were designed to protect the suspended canister from shocks, but it didn't protect the drivers from the sight of the canister. It trembled in mid-air when the ambulance rolled over a cattle guard. It swayed as the road turned. For all its sleekness, the canister had a pregnant quality. The slug deep inside it seemed, in Joe's mind, alive. It was an interesting concept, metal that was alive. Not simply a mineral capable of some sort of chemical reaction, but so alive with alpha activity that the water around the slug was warmed to 100 degrees.

"Magnificent, the sun and these Wasatch mountains." Santa twisted this way and that for better views. "You boys must love this run."

"Machine-Gun Joe was a rough and ready redskin," Joe sang softly, "He'll never let plutonium touch the ground. And he always will remember the seventh of December, With his be-bop-a-rebop and he'll blow 'em down. I'll tell you what we'd be doing if we weren't doing this run," Joe said to Ray, not to Santa. "We'd be somewhere in the South Pacific digging mass graves in a coral reef. We'd be burying bodies that were six months old, and pieces of bodies, with one dull shovel for the two of us."

"The South Pacific, you think?" Santa asked.

"Somewhere where no one would find us until the war was one year over," Joe told Ray. "We could play poker for seashells." The whites of Ray's eyes were turning from pink to acid red.

"Why us?" he demanded.

Santa was atypically silent. The convoy gained altitude at the Mormon hamlets of Orem, Provo and Helper, touched down the Colorado River at Moab and then rose again up La Sals. Ray's blood went on pooling in his eyes. He pointed out every dead rabbit carcass on the road with his Tommy gun and laughed uproariously.

The amphetamines made Ray worse, but not much worse, than the first run he and Joe had made, when Ray sobbed all the way. Ray was a primitive Sicilian, afraid of nothing in the world until he came to the Hill and underwent the safety course on radiation. With his poker winnings he could afford to pay other enlisted men to pull his hazardous duties. Ray was never within a hundred yards of radioactive material, except when he and Joe were ordered to run the slug. The convoy had stopped in Moab to eat, but Ray did not eat, drink, piss or shit and he would not until the trip was over. At least, Joe thought, the night would cool Ray's sweat and the dark would hide the canister that danced at their backs.

Darkness fell at Cortez, Colorado, on the edge of the San Juan Mountains, where the stone climbed over itself like worn steps to the waning moon. Here, the mountain building was recent and ongoing, rubbing and fraying the road to dust. Clouds swept by like steam from the engines of the earth and winds heaved stones downhill, chasing tyres and rattling on the ambulance roof. Joe followed the repair truck ahead. Its red tail-lights would disappear round a wall of stone or wink desperately as it fought a downgrade. On one side of the road was granite, on the other the unforgiving dark of an abyss. Sometimes the road lay on a ridge with a black void on either side, and there ice had chipped away at the tarmac, leaving just enough room for the truck to inch through. The wind rose with them, out of the depths below, sounding like it was pushing boulders uphill.

"Let me confide in you, men, and tell you why you're here," Santa broke the quiet, "why you were ordered to make this run again, although it's not part of your ordinary duties. You were chosen because you have higher clearances than the other drivers and you have some inkling as to the actual nature of the project and of tonight's cargo. As we approach a test shot, more and more men, enlisted men on the Hill and at the Trinity test site, will get some inkling of the nature of the project. There'll be wild stories. You may hear, for example, that Dr Teller once tried to have the project stopped because his calculations showed that one such device would set the atmosphere on fire."

"Did he?" Joe asked.

"Yes, but later calculations showed that such a danger doesn't exist."

"Hardly exists?"

"Hardly. You see, then, how these stories get started. In fact," Santa chuckled, "Dr Teller wants a bomb one hundred times bigger, so he's not afraid."

"What'd he say?" Ray came out of a reverie.

"Teller's not afraid," Joe said.

"Afraid of what?" Ray winced as Joe dodged a pothole.

"All the same, there may be apprehension among the enlisted men as more of them come into contact with this sort of cargo."