Halyna Nykolaivna begins the nine o'clock round at nine oh seven, seven minutes late because the second-floor stairway has been wet again from the rain that came in through the broken window, and before going up she had to run the mop over it. It is not a matter for her role — the window is the building's responsibility, not the concierge's — but the stairway is her responsibility, and on a wet stairway old people fall. She is sixty-six. She knows what it means to fall on a stairway.

The first floor is in the silence of Monday morning, with the doors closed and the neighbours' footsteps audible through the doors. On the second floor there is the sound of Mr Onyshchenko's television, which he keeps loud because his wife no longer hears well. On the third floor no sound. On the fourth the woman from twenty-three comes out with her shopping bag and says good morning, and Halyna answers her, and the woman goes down, and Halyna goes on.

On the fifth floor she hears the first blast. It is not the first of the war. It is the first of this morning. She knows it by the timbre — it is a full blast, not a light one — and she knows it is a missile and not a drone. Drones she no longer notices. Missiles she does. She stops on the fifth-floor landing, rests a hand on the wall. The wall trembles faintly. No one comes out of the doors. It is Monday morning. Whoever can is at work.

She climbs to the sixth. She climbs to the seventh. On the seventh the old woman from forty-two asks her if she knows what it was, and Halyna says I don't know. She does not say it to reassure. She says it because it is true. She does not know where it fell. She knows it fell close. She goes on.

On the eighth floor the corridor wall is no longer there. Not all of it: the right half of the corridor, from forty-seven to fifty-two, hangs over the void. The door of forty-seven is still in its place, but the wall beside it is gone, and through the gap you can see the sky of Kyiv, a grey sky with a plume of white smoke rising to the west. There is no dust in the air. The dust has already settled. The collapse happened an hour or two ago, perhaps more.

Halyna stands still. Then she begins the round. She has learned to do the eighth-floor round from right to left, but this morning she cannot, because the right is not there, and so she begins from the left. She knocks at fifty-three. No one answers. She knocks at fifty-four. No one answers. She knocks at fifty-five. No one answers. The doors on the left side are locked and no one answers because it is Monday morning, and she knows it, and she knocks anyway.

She knocks because the round is the round. The round is not for answering. The round is to let people know that someone passes, that someone checks, that the building still has a concierge. If a door opens she asks if anything is needed. If a door does not open she goes on. It has been like this for thirty-five years. First at number twenty-nine, Zdolbunivska Street. Then here.

When she reaches the middle of the corridor she stops in front of the place where forty-nine should be. Forty-nine is Solomiya, the twenty-four-year-old seamstress who moved in in April and asked her to keep a parcel of fabrics until she could carry it upstairs. Halyna kept it for a week, then Solomiya came by, said thank you, took the parcel. Halyna remembers that she was short. She remembers the dark hair and the voice that joked about the surname — Yakovleva, like the surname of a politician Halyna never quite worked out who he was.

She knocks at forty-nine. She knocks into the void, because forty-nine is not there. The door of forty-nine fell with the wall, and the door of fifty too. But Halyna knocks where the door of forty-nine should be, and stays a moment listening, as if someone could answer.

No one answers. She goes on. She knocks at fifty-one. It is no longer there. She knocks at fifty-two. It is no longer there. She knocks at fifty-three, which should be at the start of the right-hand corridor where it all began, but fifty-three was on the left side and is still there, and this time Halyna makes a mistake, and knocks at the door of fifty-three for the second time, because she had already knocked there at the start of the round.

The lady of fifty-three opens the door. She is in slippers. She asks if she knows what it was. Halyna says forty-nine is no longer there. The lady of fifty-three looks at her, does not understand. Halyna tells her again: forty-nine is no longer there, fifty is no longer there, fifty-one is no longer there, fifty-two is no longer there. The lady of fifty-three covers her mouth with her hand.

Halyna goes on. On the seventh floor she stops. She must go back down to the lodge to fetch the notebook with the telephone numbers and call the families. But before going down she returns to the eighth, and stops again in front of forty-nine. She knocks. She knocks softly. She does not wait for an answer. She goes down.