‘Margaret was ill,’ Vera said suddenly, realizing she hadn’t yet shared this information with Joe. It had been playing on her mind since the post-mortem, and even as she’d been listening to him. ‘Possibly terminally ill. Bowel cancer. Paul Keating thought she might not have survived very much longer anyway. I’m not sure if she’d seen a doctor. But if she knew . . . She was religious, wasn’t she? Maybe there was an idea of setting her affairs in order.’ She slapped her hands on the table in front of her. ‘I need to know where she’d been before she got onto the Metro that day.’ She stood up suddenly.

‘Where are we going?’ He hadn’t finished his tea.

‘To see Dee Robson. Alcoholic and occasional sex worker.’ Vera stamped across the wet floor to the counter and ordered a bag of cakes to take out.

The snow in the street had turned to a grey mess and it was drizzling, rain mixed with sleet. The flat was in a Sixties box, built at the end of a street of 1930s houses, and Dee lived at the top on the third floor. It wasn’t as grim as an inner-city tower block, but there was graffiti all over the stairwell and the inevitable smell of piss and damp concrete. The door looked as if someone had recently tried to batter it in. An over-enthusiastic client or something more sinister? Joe knocked. Nothing. Vera banged on the door with the palm of her hand and shouted, ‘Come on, pet. Let us in. We’re not here to hurt you.’

There was a movement behind the door, but still it didn’t open. Vera pulled Margaret’s keys from her bag and tried the one they hadn’t yet identified. The door opened. One mystery solved, then. Dee Robson stood just inside, legs apart, braced for a fight. When she saw Vera she spoke with loud and righteous indignation.

‘Hey, lady, you can’t just let yourself into my home!’

Vera took no notice and looked around her. If she hadn’t known better she’d have thought the flat was derelict. There was the same smell as in the stairwell. Mould grew where the walls and the window frames met. There was no carpet on the floor, which was sticky underfoot. Through an open door she saw the bedroom. Here there was a stained rug and a double mattress covered with a shiny pink quilt. In there Dee must entertain the men, so desperate or so drunk that they’d been persuaded home with her.