“Remember the Dragon,” Harvey said, although he hadn’t looked up from the core when Joe came in.

Joe stayed back by the wall, which was a foot thick, making the room relatively cool, maybe 90 degrees. The plastic-covered window faced the idling cars, poised for flight in case of a slip of Harvey’s hands. Joe’s mission orders at Trinity were to stay with Oppy at all times and make sure the project director survived any accident.

Harvey gave the core a final polish with an emery cloth. “I gave away my clarinet.”

“Too bad, you had great potential,” Joe said.

Harvey’s Critical Assembly team followed his every move with the intensity of chicks watching their mother turn an egg. One of them put long brass tweezers and a small shockproof case studded with plugs on the table, then unlocked the case and raised the lid. On a bed of foam rubber lay a large pearl, a one-inch ball of platinum-coated polonium. This was the core within the core, an “initiator” that would emit a burst of neutrons in the first millionth of a second of detonation.

“I think I’ll stick to what I’m good at,” Harvey said.

He reopened the larger core, propping the top hemisphere with his finger. With his free hand he picked up the tweezers and with the two brass tines lifted the tiny ball. He had to place the initiator in its nest in the center of the core, and the insertion had to be done in slow motion while the building radiation was monitored. He blinked through his sweat, but his hands didn’t falter. His finger prodded the core a little more open as the ball and tweezer advanced. The ticking of the Geiger counters rose like the pulse of excited hearts. Oppy looked as if he was going to sway and drop.

“Those icy atoms up and down my spine,” Harvey sang softly. “The blue of ions when your eyes meet mine. A strange new tingle that I feel inside, and then that radiation starts its ride.”

Oppy’s pipe hit the floor and spun across the boards. Harvey froze, fingers in the maw of the two hemispheres. “Joe, will you please take Oppy for a walk?”

Outside in the hot, dry air, Joe found his shirt had soaked through with sweat. Oppy sat on the low stone wall, hat on his knee.