‘Does my father know?’

‘Heck, no. That would have given him even more power over me.’

Her hostility had vanished, and now she just looked vulnerable. In her eyes he saw a plea, though he was not sure what she was pleading for.

He looked at Georgy with new eyes: the light skin, the green eyes, the odd resemblance to Daisy. Are you mine? he thought. Can it be true?

But he knew it was.

His heart filled with a strange emotion. Suddenly Georgy seemed terribly vulnerable, a helpless infant in a cruel world, and Greg needed to take care of him, make sure he came to no harm. He had an impulse to take the boy in his arms, but he realized that might scare him, so he held back.

Georgy put down his orange juice. He got off his chair and came around the table to stand close to Greg. With a remarkably direct look, he said: ‘Who are you?’

Trust a kid to ask the toughest question of all, Greg thought. What the hell was he going to say? The truth was too much for a six-year-old to take. I’m just a former friend of your mother’s, he thought; I was just passing the door, thought I’d say hello. Nobody special. May see you again, most likely not.

He looked at Jacky, and saw that pleading expression intensified. He realized what was on her mind: she was desperately afraid he was going to reject Georgy.

‘I tell you what,’ Greg said, and he lifted Georgy on to his knees. ‘Why don’t you call me Uncle Greg?’

(iv)

Greg stood shivering in the spectators’ gallery of an unheated squash court. Here, under the west stand of the disused stadium on the edge of the University of Chicago campus, Fermi and Szilard had built their atomic pile. Greg was impressed and scared.

The pile was a cube of grey bricks reaching the ceiling of the court, standing just shy of the end wall which still bore the polka-dot marks of hundreds of squash balls. The pile had cost a million dollars, and it could blow up the entire city.

Graphite was the material of which pencil leads were made, and it gave off a filthy dust that covered the floor and walls. Everyone who had been in the room a while was as black-faced as a coal miner. No one had a clean lab coat.

Graphite was not the explosive material – on the contrary, it was there to suppress radioactivity. But some of the bricks in the stack were drilled with narrow holes stuffed with uranium oxide, and this was the material that radiated the neutrons. Running through the pile were ten channels for control rods. These were thirteen-foot strips of cadmium, a metal that absorbed neutrons even more hungrily than graphite. Right now the rods were keeping everything calm. When they were withdrawn from the pile, the fun would start.

The uranium was already throwing off its deadly radiation, but the graphite and the cadmium were soaking it up. Radiation was measured by counters that clicked menacingly and a cylindrical pen recorder that was mercifully silent. The array of controls and meters near Greg in the gallery gave off the only heat in the place.