The lobby of Halvard Tower had forty-one cameras, and Nia Boateng had counted all of them before the revolving door finished its turn.

Eleven were obvious: black domes in the ceiling like a row of closed eyes. Nine were disguised as smoke detectors. Six sat inside the brass trim of the reception desk. The rest she found by the way the marble had been cut around them, one clean square at a time, as though the building had been taught to grow ears.

She stood on the carpet strip marked VISITORS and held a cardboard coffee cup in one hand and her work bag in the other. She looked like a woman who was early. That was the whole of the disguise.

Her phone buzzed against her hip. She let it. It buzzed again. On the third time she took it out with her thumb, the way you take a splinter out.

PINKY: ARE YOU INSIDE PINKY: blink twice if they've taken your phone PINKY: also you have a 9am with Gerald Pruitt and I want a full report on his tie

Nia typed: In the lobby. Phone not taken. Tie unknown.

PINKY: you're so calm it's frightening me PINKY: eat something

She put the phone away. Calm was a skill, like picking a lock. It was not the same as feeling nothing.

The desk was a long curve of pale stone. Behind it sat three people in charcoal blazers, each with the polite, pressed look of someone who had been told the building listened. A fourth stood at the end, not behind the desk but beside it, with his hands loose at his sides. He wore the same charcoal as the others but he did not wear it the same way. He watched the room the way other people watched a phone.

"Name?" asked the woman in the middle. Her badge said TUNDE OYELARAN, which was either a family joke or a clerical mistake. Her voice said she had been asked the same question nine hundred times a week.

"Nia Boateng. Kestrel Recovery. I'm expected on thirty-four, finance, nine o'clock."

"Photo ID."

Nia handed over her driver's licence. It was real. Everything she had was real; that was what made it hard to catch. The surname on it had been hers for eighteen years, longer than the first one. The first one she had never once said aloud since she was eleven years old. Not in the shower, not drunk, not to Pinky. She kept it the way you keep a receipt for something you intend to return.

"Kestrel," said Tunde, scanning. "The collections people."

"Recovery," said Nia.

"Same dentist, different chair." Tunde's mouth tipped. She did not look up. "Rule of the house, Ms. Boateng. You get a badge. The badge opens the doors we say it opens, and it remembers every one. You're on thirty-four and the lift to thirty-four. Anything else, you ask, and somebody walks you. Nobody goes anywhere in this tower without being counted."

"I like being counted," Nia said, and for once it was not entirely a lie. It was how she made her living.

The printer under the desk gave a small whine. The badge came out warm, a white card with a green stripe and her photo, taken a second ago without her noticing. The camera in the brass trim. Seventh from the left. She hadn't clocked that one, and it irritated her.

"Thirty-four," said Tunde, sliding it over.

"Hold on."

The voice was quiet. Nia turned her head only as far as politeness required.

The man from the end of the desk had come closer. Mid-thirties, she judged, dark hair kept short, a face made of straight lines with one exception, which was his mouth, which looked as though it had just decided not to say something. His own badge hung low on his lapel. RAFAEL MIZRAHI-DUBE. HEAD OF SECURITY. FLOOR 38.

Thirty-eight. The Quiet Floor. It wasn't on the lift buttons she had been shown on the blueprints Kestrel was given. It was in every other document she had ever read about the place, spoken of in the tone people used for a dentist's drill heard through a wall.

"Rafi," said Tunde, lightly, a warning in it that Nia pretended not to hear. "She's cleared."

"She is. I just like to say hello." He looked at Nia. His eyes were the brown of strong tea, and they didn't blink at the usual interval. "Rafael Mizrahi-Dube. I look after the building. Ms. Boateng, welcome."

"Mr. Mizrahi-Dube."

"Rafi. Everyone gets tired of the rest." He held out his hand, and she shook it because refusing would have been interesting. His grip was dry and brief. His eyes went to her coffee cup, then her bag, then her face. "You were counting."

Nothing in Nia moved. That was the training.

"Pardon?"

"When you came in. You looked at the ceiling, and then you looked at the desk, and your lips moved. I thought you might be praying, but you didn't look afraid." He tilted his head. "Forty?"

"Forty-one," said Nia, because the truth, offered cheerfully, was the best lie she owned. "Occupational habit. I count exits, I count staff, I count how many people in a meeting are lying. It stops me from being bored."

"How many in your last meeting?"

"Three. Out of four. The fourth was asleep."

The corner of his mouth made a small, fast movement and was gone. "Forty-one is correct. Nobody has ever said forty-one." He seemed less pleased than interested, which was worse. "Most people stop at the dome ones."

"Most people aren't paid by the hour to find things people have misplaced."

"Is that what you do?"

"I find what people owe," said Nia, "and then I ask politely."

"And if they don't pay?"

"I ask again, in writing."

Tunde laughed once, a short surprised sound she smothered. Rafi did not laugh. He held Nia's gaze a half-second longer than the joke required, and Nia felt something she had not planned for: the sense of being priced. Not looked at. Priced. She knew the feeling from the other side of the table, and she did not enjoy it.

"Thirty-four's expecting you," he said. "Tunde, run her name through the visitor archive before she goes up. Housekeeping. I want it clean for the audit."

"It's been run, Rafi. Twice. HR and procurement."

"Run it through the old archive. The pre-migration one."

Tunde sighed, the sigh of someone with a queue. "That's ancient. Nobody's done that since the merger."

"Then it will be quick."

Nia kept her face where it was. A routine check, she told herself. A tidy man making a tidy gesture. There was no reason for her pulse to start doing arithmetic.

She watched Tunde's fingers move across the keyboard. A green cursor blinked on a black screen the building had never quite let die. A progress bar crept. On the wall behind the desk, a screen showed a looping film of the Halvard cranes in the port at Hamilton, orange against a fake sunrise, the family name in a clean white sans-serif: HALVARD. Moving the World's Weight. Under it a single date: Est. 1971.

Her grandfather's cranes. Her father's name had been painted on one of them, once. Somebody had sanded it off.

"Huh," said Tunde.

"What?" said Rafi.

"One hit. Old guest log." She frowned at the screen. "Weird format. It's pre-migration, so it's just a flat text entry. Visitor, N. Boateng, minor. Accompanied by I. Boateng, adult. Signed in 11:48 p.m." She scrolled. "Signed out 1:20 a.m. Same night. Sponsor field says, um. Restricted. Floor access, forty."

The coffee cup in Nia's hand stayed exactly as steady as before, and she was proud of that, in a distant way, the way you are proud of a limb you cannot feel.

"What's the date?" said Rafi. He wasn't looking at the screen. He was looking at her.

Tunde read it aloud. "Fourteenth of March, 2008."

Nia had a very clear memory of the fourteenth of March, 2008. A Friday. She had been eleven, in bed in Ines's spare room in Scarborough, listening to the radiator and the sound of her mother, who was not yet her mother, walking the corridor in the dark. In the morning there had been a different house and a different name. She remembered being told: We were never at that building, Nia. Not that night. Not any night. You were asleep. Her whole childhood had been built on that sentence, a floor you stand on without wondering what is underneath it.

And yet here was the floor, in green letters, with a hole in it.

The thing nobody tells you about a lie is that it has a timestamp.

"It's a coincidence of surnames," Nia said, and heard her own voice come out as pleasant as warm milk. "Boateng's common. I can think of a dozen. My mother cleaned half the office towers in this city when I was small."

"Did she clean this one?" said Rafi.

"She never mentioned it."

"Never?"

"I was eleven," said Nia. "I mostly remember snacks."

It was a joke, and she delivered it as one. But she saw him file it. He didn't write anything down; he didn't need to. The file in his head had a drawer for exactly this, and she had just been put in it.

"Of course," he said. "Boateng is common. I'm sorry. Old habit." He took a step back, and the room's air resettled. "Thirty-four, Ms. Boateng. Mr. Pruitt will be waiting. He likes people on time."

"So do I."

She turned toward the lifts. The walk was thirty-one steps across the marble. She counted them, because it was something to hold. At step twelve the screen over the desk changed to the weather. At step twenty her phone buzzed again, and she did not look at it.

At step thirty she let herself think the thought she had been holding off the whole way across the lobby, the one that sat on her chest like a coin on a dead man's eye.

Eighteen years she had believed that Ines Boateng had never been inside this building after the night her father fell. Eighteen years she had believed that her name was a thing the Halvards gave away afterward.

But the name was on the log the same night. Before the sun came up. Before the policy, the settlement, the paper with the signature, the lawyers.

Which meant someone had known what her name would be before her father was dead.

The lift doors opened for her with a polite chime, and in the brushed-steel wall of the car her own face looked back at her, calm and a little pale, with her mother's eyes and her father's jaw. She pressed 34.

The doors began to close. Across the lobby, beside the desk, Rafael Mizrahi-Dube was still standing where she had left him, not looking at the screen anymore, but at the lift. At her.

He lifted two fingers to his temple in a small, grave salute.

Then the steel came together, and she was alone with the number on the display climbing, and the first name on her Schedule waiting at the top of it, and a new line on the page she had never meant to write.