The fog came down the valley like a living thing, thick and yellow and smelling of coal smoke and wet stone. Thomas Blackwood stood at the edge of it and looked at the wall.

It had been there seven years now, though no one called it that anymore. It was the Quarantine Barrier. It was the Great Separation. It was the thing that divided the living from the dying, the clean from the infected, the fortunate from the unfortunate. Thomas knew which side of it he had been born on, and which side he had spent most of his life on.

Both sides, in the end.

He stood at the gate—a massive iron thing, rusted at the hinges—and looked through the bars at the street beyond. The street was empty. It was always empty. Seven years of empty. Seven thousand four hundred souls, according to the ledger he had seen in the surgeon's study, where he had no business being and from which he had been thrown like refuse.

"Tom."

He turned. Sarah stood behind him, small and dark-eyed, her hands clutching the hem of a dress that had belonged to someone else's daughter. She never spoke. She had not spoken since he pulled her from the workhouse pit, where they had been piling the dead like cordwood and calling it economy.

"I know," he said softly. "I know what it says."

The letter in his pocket was heavy. He had read it fourteen times. Fourteen times the words had meant the same thing: Thomas Blackwood, by order of the Royal Academy of London, you are hereby recommended for admission to the Institution, in recognition of your distinguished service and demonstrated courage during the northern campaigns.

Distinguished service. He had killed three men with a bayonet and called it service. He had marched through fog and mud and called it duty. He had done all of it thinking it would lead somewhere—anywhere—other than back to this wall, this terrible stone monument to the lie that keeping people apart was the same as keeping them safe.

The surgeon had tried to tell him. Old Dr. Whitmore, who had pulled him from the pit and fed him broth and read him passages from Milton when the boy couldn't sleep. The old man had found the records, hidden behind a loose stone in his study, and when he had confronted the Governor, they had found Whitmore floating in the river three days later.

Accident, they said. Drunk. Fell in.

But Whitmore had not drunk in twenty years.

Sarah tugged his sleeve. She was looking at the wall, her small face pale in the fog. He knelt beside her and took her hand. Her fingers were cold.

"They're not sick, Sarah," he said. "None of them are sick. The miasma is a fiction. The wall was never built to keep disease out. It was built to keep people in."

Her eyes were wide. She understood more than most children her age. She had seen what he had seen—had seen it with him, in the pit, in the workhouse, in the streets where the poor were rounded up like cattle and pushed through the gate into a world that would never let them out.

"What do we do?" Her lips moved. The words did not come out, but he knew her. He had known her for four years. He knew every expression on her face like a book he had read a hundred times and still found something new.

He stood up. The letter felt heavier in his pocket. The Academy. London. A future. Everything he had worked for, everything Whitmore had believed in him, everything he had endured the pit for.

And everything that was built on a lie.

The gatekeeper watched him from his post. A fat man in a uniform that had once been respectable. He did not try to stop him. No one did. The wall had rules, and the rules were simple: once you were inside, you could not leave. Once you were outside, you could not enter. But the rules said nothing about standing at the gate and thinking.

Thomas thought.

He thought about Whitmore's hands—shaking, old, but steady when they held a pen. The way the old man had written those records, knowing what would happen, knowing that truth was a luxury the powerful could not afford.

He thought about the seven thousand four hundred names in the ledger. Seven thousand four hundred people behind that wall. Most of them had never been examined by a physician. Most of them had never shown a symptom of anything except poverty.

He thought about Sarah.

If he left, she would come. She always would. She was nine years old and she had no one else. But the Academy—what would it do with a mute girl? What would it do with a boy who had crawled out of a pit and carried a sword for the first time at fourteen?

They would take him for his merit, not for who he was. They would use him. They always used people like him.

The fog thickened. The wall disappeared into white. Thomas could no longer see the other side.

He reached into his pocket and took out the letter. The paper was fine—imported, expensive, the kind of paper that belonged to a different world from the one he lived in. He held it over the muddy ground and looked at it for a long time.

Then he tore it in half.

Sarah watched him without comprehension. He tore it again. And again. Until there were only small pieces of fine paper in his hands, and he let them fall into the mud.

"I'm not going," he said.

Sarah's eyes widened. She grabbed his coat. She shook her head. She did not understand, but she understood enough.

"I'm staying," he said. "With them. With you."

The gatekeeper shouted something. A carriage was approaching—black, official, with the Academy's crest on the door. They had come to collect him. They had come to take their recommended boy to London and use him for whatever purpose the Institution had decided he was worth using.

Thomas picked up Sarah's hand. He turned his back on the gate. He turned his back on the carriage. He walked toward the wall, toward the gate that only opened outward, and he knocked.

No one came. No one ever came to the gate from the inside. They knew the rules. Once you were in, you were forgotten.

He knocked again. And again. And on the third knock, something moved behind the stone. A face appeared at a small slit he had never noticed—a ventilation opening, or a viewing port, or a place where someone had pressed their eye to see the world they had been denied.

A woman's face. Old. Terrified. Grateful.

Thomas pressed his palm against the stone. Sarah pressed hers beside it.

Behind them, the carriage turned and left.

The woman's name was Margaret. She had been behind the wall for three years. She had been a teacher before the quarantine. Before the lie. Now she was one of seven thousand four hundred names in a ledger that no one would ever read.

She opened the gate a crack. Just enough for two small figures to slip through.

"Thank you," she whispered.

Thomas looked back at the wall one more time. The fog was closing in. The gate would be sealed within the hour. He would never see the outside world again.

He turned to Margaret and Sarah and said the words that Whitmore had once told him, words from a book the old man had read by candlelight when the boy couldn't sleep:

"I would rather rot in truth than be saved in their lie."

Inside the wall, the seven thousand three hundred and ninety-nine turned to look at the two new faces. Some wept. Some were silent. Some simply stared, as if seeing human beings from the outside was something they had forgotten was possible.

Thomas Blackwood stepped through the gate and did not look back.