“The first time? On a boat,” he said. “We were on a boat. There was a terrible storm. Forty of us, maybe more, trapped like cattle on our way to the slaughter, showing the whites of our eyes.”

“When was this?” I said.

“I was about your age. I was practically brand-new. I remember the horizon. Blue on blue, and nothing else, in a fine, straight line. I let myself stretch out along it. I made my mind wire-thin.”

I thought of the moment, only hours ago, on the dark beach when I couldn’t tell them apart, the sky and the sea.

“The edge of things,” Novo was saying. “The line between.”

“I couldn’t think how far away it was, as far as the eye could see, and afterward I learned the equation by heart: 1.22459√h, where h is the height above sea level. The distance that first time was about four miles. But the line itself is endless.”

“Yes,” Novo said.

Henry narrowed his eyes as if he could still see it. “Sun on its decks, all that red metal crusted with rust and bird shit. The sky above us was thick with gulls. There was no sign of the storm.”

He bowed his head. “When all around you is water, and all you can hear and smell and feel is the boom and stench and weight of water throwing itself against you, you forget everything.”

Novo reached out and took his hand, and that’s when I felt it, this dank, dead cold lapping at my ankles, and when I looked down, the floor was moving, soupy with murk and bird droppings and the glinting scraps of dead fish, like the bottom of a boat.

“What’s happening?” I said, and Novo’s grip tightened on Henry Lake’s hand.

“Just a memory,” he said, his other arm still round me. “Not real. Not now. I promise.”

He closed his eyes but I kept mine open while the whole room peaked and dropped on those remembered waves, over and over, the walls outside battered by great punching gusts of wind, the rain that landed on the windows deafening and relentless. I watched it all.

“Only two things were sure in that moment,” Henry said. “My death and the water. I tried to picture the world without me and it was easy. I knew the world wouldn’t notice. I wondered if there was anyone on that boat the world would miss. I thought about them all dying and their families never knowing, only picturing them alive and well, and if that would make a difference, if that would keep a part of them alive and well somewhere after all.”

“I’ve thought that,” Novo said. “I’ve wondered that.”