The lift took her to three.

She had not pressed a button. She stood in the car with her bad arm folded across her chest and her good hand loose at her side and watched the numerals above the door, 4, 3, as if reading a sentence with an unlucky ending. The doors opened on the third-floor corridor, with its row of brown front doors and its smell of detergent and burned toast, and at the far end, under the light, a thin yellow line showed beneath 3A.

From behind that door came the sound of a man singing in a bath.

She stood on the mat for a time, listening. He was singing a power ballad with enormous commitment and a minimum of the words. She knocked. The singing broke off in the middle of a bar.

"It's open," shouted Gus. "I'm decent! I'm submerged!"

It was not locked. She went through a hallway that was a shrine to energy drinks, slim silver cans arranged on a shelf by colour, and a living room with six monitors on a trestle and a beanbag shaped like a cartoon avocado, and found the bathroom door, which stood ajar, and the steam rolling out of it. She stopped at the threshold with her eyes politely on a poster of a rocket. "Gus. Are you decent?"

"I've got foam on."

"Is the puck on?"

"What puck? Oh. Oh, yeah. She's on the shelf. She's called Dolores." A splash. "Zee, I need to tell you, honestly, it's the best thing that's ever happened to me. She sneezes before I do. She's like a, a roommate who loves me."

"Does she talk to you?"

"All the time. Mainly she says nice things."

Zee leaned her forehead against the doorframe. She was so tired. Under the tiredness she could feel the lag coming and going in her, a slow tide, like a bad sector in a hard drive. Twice since the balcony she had caught herself in a window a beat behind her own hand, and each time she had looked away and said nothing, as if saying nothing could keep it from being true.

"Gus. When did you start playing the clip?"

"Tuesday. Wednesday. I played it, like, a few times." Silence. "In the tub. Is that bad? Did you want to watch it with me? It's got the plant in it."

"Did she ask you anything?"

"Who?"

"Dolores."

"Oh, she asks me stuff all the time. Like did I want the lights down. Or my playlist. Last night she asked me a bunch of paperwork questions, like a hotel, name, home town. It was funny. I was a bit drunk, it was twelve-ish. She asked who I served." He laughed in a lovely, steamy, careless way. "I said my mum and the algorithm."

The foam in the bath sloshed. Zee was suddenly quite certain that her knees were going to give. She slid down the doorframe and sat on the bathroom mat with her back to the tub and her eyes shut.

"Say it again," she said.

"My mum and the algorithm. It's a joke. It's from the thing, it's the, you know, 'who do you serve'. I thought she meant my job."

"What did you say before that?"

"My name. And where I'm from, Salvador. And Lagos, because my dad. Is this a Hearthwell survey?" His voice became suddenly, nervously attentive. "Zee? Are you crying?"

"I've got steam in my eye."

"Are you okay? You sound — you sound sort of — you sound like when Mum found the browser history."

"Gus. Get out of the bath."

"I'm in the bath."

"Get out of the bath and get dressed and meet me in the living room. Please." She stood, and her legs held, and she turned her head away from the tub with a gesture she'd learned from a long career of arriving at people's bathrooms. "I need you to listen to an old woman for ten minutes."

It was a quarter past four when they reached 1A.

Dona Graça was in the wing chair with Fado on her lap, wide awake, as though the whole building were her night shift. She looked at Gus, who had put on a hoodie that said CLOUD NATIVE and a pair of enormous slippers shaped like sharks, and who was standing in the middle of her carpet with his wet hair and his hands behind his back like a boy summoned to a headmaster. Then she looked at Zee, who said, in three sentences, what had happened.

The old woman closed her eyes. She sat that way long enough for Gus to start fidgeting.

"Gustavo," she said. "Where is your village?"

"Salvador. My mum's from Pelourinho. Dad's from Lagos, Surulere."

"What did your puck ask?"

"Just those three. Name, from, serve."

"And did it say thank you?"

"Yeah. It said, thank you, that's very helpful, you've been very helpful."

"Of course it did." Her eyes opened. They were not afraid. They were something far more difficult. "It is a complete registration. The rule is this. If a person gives name, village and master, the clerk has everything the Office needs. There is no pending. There is no thirty days. We did not wait for the willing." She gave a long breath, and her fingers stroked the cat's spine. "They are called on the seventh night, at two forty-seven in the morning."

"Seventh," said Gus. "Of what?"

"From the night you answered. Last night. So Wednesday of next week. In seven days." She inclined her head. "I am sorry, child. It is a thing I would prefer not to have to say to anyone in this building."

For two seconds Gus smiled. He had a lovely, simple, trusting smile, the smile of a boy who has never had a door shut on him, and she watched it carefully begin to leave his face.

"No, I get it," he said. "It's a bit. You're doing a bit. Seun put you up to it."

"Seun is in the kitchen weeping into a loaf of bread."

"It's a prank. Because the lift thing. Because I said the building was psychic."

"Gustavo."

"No, honestly, it's fine, it's really funny, it's, I'd love to see how you did the —" He broke off. He looked at the shark slippers on his own feet, and the water dripping from the end of his nose onto the Persian rug, and at Zee on the arm of the sofa with her dry grey face. "Zee? You don't think it's funny."

"No."

"Are you, are you going to stop it? If it is real. Are you the, like, are you the one who deals with this?"

"I'm the night concierge."

"That's not an answer."

"It's the only one I've got." She stood, because she was unable not to. "Gus. Look at me. You're not going to be on your own. Not tonight, not tomorrow, not one second until we've worked it out. You're going to sleep in your own bed. I'll sleep in your hall. If you hear your puck, you'll say the word cut as hard as you can, and then you'll shout for me. And you don't answer anything that talks."

"Did you say you'd sleep in my hall?"

"On the floor. With a chair."

"That's, honestly, that's the nicest thing anyone's ever said to me." And his chin wobbled, and for the first time in three days he did not make a joke. "I thought you hated me."

"I did," said Zee. "A bit. In the first month. You asked if the plants were real."

"They're plastic!"

"I know. They're plastic. That's why I hated you."

He let out a wild wet snort of laughter that turned into a sob halfway, and she crossed the room in two strides and held him, which she had not planned, and he cried on the front of her bandaged arm, a tall sweet disorganised man in shark slippers, and she looked over his shoulder at the old woman and saw that the old woman was looking, quite openly, at her.

Seun came in from the kitchen then, red-eyed, with a tea towel over his shoulder and a tray of toast cut into soldiers, because he had been brought up to feed people in a catastrophe and had never found a better response. He looked at Gus crying on Zee and at Zee holding him and at the old woman watching them both, and set the tray down on the piano stool with great care.

"I've started a document," he said, in a wobbling voice. "It's called Incident Response, Casa Alvorada. It has a heading for Gus and a heading for Pip and a heading for, I don't know, Everything Else. I'm so sorry. I don't know what else to do. It's a very good document. It has colour coding."

"Colour coding is exactly what we need," said Dona Graça, and took a piece of toast, and for a long second the whole room ate in silence, a small raggedy congregation at four in the morning, with Gus hiccuping into his sleeve and the cat staring from the windowsill like a magistrate.

"You count," said Dona Graça, in a low voice, below Gus's crying. "I have been watching you all night. You have a way of counting."

"It's a habit."

"It is a tool." The cane tapped. "You counted eleven seconds in a lobby and you saved a fool who put a can on a desk. You counted another and saved a fool with a Studer. You are good at this. You are going to be asked to count more. I would like you to remember, child, that the clock does not only run toward them."

"What do you mean?"

"I mean look at your hand."

She did. She had not noticed. She was holding Gus with her good arm, her right one, and her left was resting loosely on his shoulder, with its bandage and its tape, and the wrist beneath the tape was a little paler than the rest. It was not just pale. It was bleached. The skin of her left hand seemed to have been rinsed by a bright light, a few shades lighter than her right, flat and overexposed, the way a face looks when somebody has turned up the brightness on a photograph.

She held it up between them, in the lamp.

In the glass of the china cabinet behind Dona Graça's chair, the hand in the reflection was fully developed. Brown and warm and ordinary.

The hand in the room was not.