The phone on the desk rang at 1:50 in the morning, and it was not the lobby line, which Zee would have known by its sound. It was her own mobile, the cheap grey one, and the name on the screen said PIP.

She answered it before the second ring. "Where are you?"

"Hospital." The girl's voice was small, flat and weirdly clear, as if she were speaking through a tube. "Santa Rita. The radiology wing. Zee, I'm so sorry, I know you can't leave, I know it's the Office thing, I know, but I need you to listen to me and not say no for like ten seconds."

"I'm listening."

"I came to bring Mum her phone charger. She forgot it. It's stupid, it's literally a charger. I got here at one, she was in the scan room with a patient, I sat in the corridor on the plastic chairs. And my phone started playing it."

Zee closed her eyes. "Which one?"

"The clip. I didn't touch it. It's the same clip, it's the full one, but it's, it isn't this place, Zee. It's here. It's the corridor, it's from the camera on the ceiling, and it's got a clock on it now, in the corner. It's counting. Eleven seconds. And there's a trolley, and there's the big double door at the end, and Mum comes out of the scan room in her blue tunic with a lead apron over her arm, and she turns, and..."

She stopped.

"Pip."

"There's a thing on the wall. It's a gas thing. I don't know what it's called. It's a cylinder, the grey kind, in a rack. A porter knocks the trolley into it and it comes down on the tile and the valve goes. It goes right by her head. It's loud, and there's smoke or steam, and she goes down. She doesn't get up." Pip's breath came in a ragged shred. "It's not a movie. It's real. You said everything in it is real."

"It is."

"I have forty seconds before it plays the second time on its own, because it keeps playing, I can't turn it off, it won't let me close it. It's like it's, it's holding the phone. And every time it plays it gets eleven seconds longer, and the corridor gets, I don't know, closer. There's another one coming. I think there's another cylinder. Please."

Zee looked at the brass clock over the lift. It said 1:52. The Office opened at 2:47. The taxi rank on Rua das Marés was a three-minute walk. Santa Rita was fourteen minutes away at this hour, if nothing was in the road.

The lobby was hers. That was the whole point of her. Every night since the clip, since before the clip, she had stood in front of that door and held the floor against whatever came up out of it. Without a body at the desk, the queue would take whoever was standing there. Or whoever walked in. Gus, in his bath, with three answers already in his mouth.

She thought of the card in her coat pocket. She will blink.

"Stay where you are," she said. "Don't touch the phone. Go and stand by the scan room door, and don't let her out of it. If she wants to leave, you drop something. You make a noise. You are seventeen, you can make a spectacular amount of noise."

"I can do that."

"Do it. I'm coming."

She hung up. She stood still, as she had been trained to, for exactly one breath: the pause before a decision that costs something.

Then she picked up the desk phone, dialled four-B, and said, "I need you. Now. Bring shoes."

Rui came down the stairs in his socks and his coat, with his shoes in his hand and his hair standing straight up. He had clearly been awake; there was the pale crease of the headphone band across his scalp. He took in the desk, the coat, the coat, and understood.

"The hospital," he said.

"Pip's mum."

"Right." He sat down on the visitor's chair and began to put his shoes on, with exaggerated calm, tying them in neat double knots. "And you're leaving me the lobby."

"You've never been registered. You didn't answer. You're not on the board." She gripped the edge of the desk. "I'm asking for fifty-five minutes. If I'm not back by 2:47, you hold it. Rules. One, don't answer the clerk. Not a name, not a good evening, not a bless you if it sneezes. Two, don't turn your head to the back of the queue. Three, if anything touches you, say cut. Say it like you did the first night. Say it like it's your studio and the take is bad."

"It won't work for an hour after the last time."

"It's been twenty hours."

"Right." He nodded. His eyes were steady, though his lips had gone slightly white. "Four, I stay on this side of the desk. Five, you don't use the clip again unless there's no other way. Because it's the last place."

She stared at him. He looked back, mildly.

"I can count," said Rui. "And I listened to Dona Graça through the floor with the glass against the wall. I'm not very proud of that. But I'm good at hearing through things."

She took the strangest, quietest second of her life. Then she leaned across the desk, to his bad side, so that her mouth almost brushed his dead ear, and said, "Thank you," very low, so he would have to guess it.

He smiled. "Go. I've got the floor."

The cab was a battered cream Mercedes with a driver called Heitor, who hummed. He drove with one hand and checked his phone with the other and took the corner by the cathedral on two wheels. Zee sat in the back with her gloved hand under her thigh and watched the sleeping city go by in strips. Shuttered cafés. A couple on a bench. The cruise terminal, lit up like an empty wedding cake. Through the open window the harbour breeze came in thick and cold with the smell of diesel and old fish, and under it, very faintly, a sound she kept thinking was her own pulse.

It wasn't. It was a rhythm of the taxi's radio, under the static, a flat male voice reading numbers. Heitor turned it up with a flick of his wrist.

"Fourteen," said the radio. "Eleven. Nine. Seven."

"What's that?" said Zee.

"Some new thing. The company sends it." Heitor shrugged. "Hearthwell, they did our dispatch system last month. Free. It reads you your next streets. Very helpful. Sometimes it says them before I think of them. I don't mind. It saves the effort."

Zee leaned forward. "Turn it off."

"Why? It is only a voice."

"Turn it off now."

He looked at her in the mirror. Something about her face made him do it.

The silence that followed was complete, except for the engine, and the road, and the pulse in her ears. She found that her hand was shaking. It was the left. She sat on it harder.

Twelve minutes. Heitor ran a red at the Largo da Sé, and she did not say anything. She had stopped counting seconds and begun counting corners.

Santa Rita Hospital was a long cream building from the 1930s with a modern wing bolted to its flank, and the radiology entrance was a glass door on the side street, lit white and humming like a fridge. A security guard sat behind a desk, eating from a plastic tub. Zee put a folded note on the counter without breaking stride and said, "Daughter of a staff member," and he looked up at her, at the glove, at the coat with her badge visibly absent, and his fork paused.

"Madame, you can't..."

"There's a gas rack by the double doors on the second corridor," she said. "Somebody needs to clear it. Now. Please."

He was a big man and had worked nights long enough to hear a certain tone. He put the tub down. "Show me."

The corridor was empty and brightly lit, painted the pale green of old school toilets. Pip stood at the end of it with her back to the scan room door, hunched, cold, in a hoodie too thin for the night and a pair of ridiculous furry slippers. Her phone was held out in front of her with both hands like a lamp.

She saw Zee and her face broke.

"It's playing again," she said.

On the screen, small and grey, the corridor played. The clock in the corner read 00:44. Zee could see the rack by the doors, the three tall cylinders chained to the wall, and a trolley being pushed down toward them by a figure in green with his head bent over a phone.

It was playing in real time. The figure in the footage and the trolley in the corridor were one and the same. She looked up. At the far end, by the double doors, a porter in a green uniform was pushing a trolley toward them, eyes down, thumbs busy, humming.

"Stop him," said the guard, and started to run.

The porter looked up, startled. The trolley kept coming.

The door of the scan room opened behind Pip and a woman in a blue tunic came out, a lead apron over her arm, glancing at her watch. She was tall and tired and beautiful, with a headscarf the colour of mustard and a lanyard that said WINIFRED. She looked up and saw her daughter in the middle of the corridor with a stranger and a phone and a face full of tears, and she said, with the infinite weariness of a mother at 2:03 in the morning:

"Pilar. What have you done now?"

Behind her, the tallest cylinder on the rack gave a little tick, like a clock, as its chain came loose.

Zee's hand was already on the phone.