She told herself she noticed him because the building was quiet.
Third floor, the flat on the left. She was fifth floor, and the building was old enough to carry sound in ways its architects had not intended.
She could hear him. Not clearly. Not words. But the rhythm of someone who worked from home: morning coffee, calls mid-morning, then quiet, and then music. Always eventually, a piano.
She told herself that was why.
The first time she'd seen him properly was in the lobby, both of them collecting parcels from the post boxes with keys that never quite fit on the first try.
She learned his name from the label. She was not proud of this.
Marcus, the label said. Flat 3L.
She began paying attention to the timing of his arrivals and departures the way she might pay attention to weather, without deciding to, not quite consciously.
She was a person who had started timing her coffee breaks to coincide with the sound of his door.
This was the arrangement. It would have continued indefinitely.
And then, on a Wednesday evening in November, someone knocked on her door.
She knew, before she opened it.
"I think we have each other's post," Marcus said, holding up an envelope.
She took the envelope. She looked at it. She looked at him.
"Thank you," she said.
"Of course." He didn't move.
"I've been meaning to knock for a while," he said.
The hallway was not large, and he was close enough that she could see the collar of his shirt, slightly worn at the edge.
The envelope was just an excuse. They both knew it already.