The laboratory door had not been opened in three years. Arthur Pemberton stood before it now, his hand resting on the brass handle, cold enough to burn. The air in the hallway smelled of coal dust and something else—something sharp and chemical that made his eyes water. He turned the handle.

The room beyond was exactly as his father had left it. Glass cylinders lined the walls, some cracked, some still containing yellowish fluid. Workbenches were scattered with papers, most of them covered in his father's cramped handwriting. And on the central table, six leather-bound journals, stacked neatly, as if waiting for someone to read them.

Arthur sat down and opened the first one.

The first entry was dated March 12, 1841. "If I succeed," it read, "the world will no longer need adults. The gas is ready. It targets only those past the age of forty-five. The young will inherit everything."

Arthur closed the book. He was seventeen years old. His father had been forty-eight.

He opened the second journal. The entries grew darker. The government had known about the project. There were memos, approvals, signatures of men Arthur recognized from the newspapers—ministers, generals, men who had vanished along with everyone else. The gas had been tested in a single factory in Manchester. All forty-three adult workers had died peacefully. The children who worked there had been given a day off. They had celebrated.

The third journal contained a map. Arthur traced the lines with his finger—pipes, he realized. His father had designed a system to distribute the gas through London's existing heating network. The city's central furnace, the one that warmed thousands of homes, had been modified. Someone had turned it on.

Arthur's hands were shaking. He forced himself to continue.

The fourth journal was different. The handwriting was worse—shaky, desperate. "I tried to stop it," his father had written. "But they would not let me. They said the project was too far advanced. They said the children were already waiting. God forgive me, I think they were right to wait."

The fifth journal contained a single page. "Phase Two," it read. "The control gas. Designed for the adolescent population. Will be distributed through the water supply. The formula is in the steel cylinder beneath the laboratory floor."

Arthur looked down. There was a grate in the floorboards, slightly displaced. He pried it open with a chair leg. Below him, in the darkness of the cellar, something metal glinted.

He went down with a candle. The cylinder was indeed there, sealed with wax and stamped with his father's initials. He carried it upstairs and set it on the table beside the journals. Six journals and one cylinder. The complete architecture of a world destroyed and another one designed to replace it.

Arthur sat in the laboratory until dawn. He read every word his father had written. He learned that the gas had been intended as a replacement—a way for children to take over industrial production without adult supervision. He learned that the government had expanded it to a global scale, using shipping routes to distribute the formula to laboratories in every major city. He learned that his father had discovered Phase Two and tried to destroy the research, but it was too late. The furnaces had been lit. The ships had sailed. The world had ended while children slept.

At dawn, Arthur carried the cylinder to the Thames. The fog was thick, the kind of London fog that swallows sound and light and memory. He dropped the cylinder into the water. It sank without a ripple.

He returned to the laboratory and set it on fire. He watched the journals curl and blacken, the pages catching flame one by one, his father's words turning to ash. He did not save a single page.

When the fire was done, Arthur stood in the fog and watched the smoke rise. The city around him was silent. No carriages moved. No voices called out. Only the wind, and the fog, and the boy who stood alone in the ruins of a world that had ended without anyone knowing why.

The fog rose from the river and swallowed everything. He stood in the fog, the last person who remembered the truth.