‘Stephen Elton works for the Ford dealership in Kilburn. He’s some kind of mechanic. Gemma Crowther works . . . worked for an alternative health centre in Swiss Cottage called The Healing Rooms. My friend visited her there. She gave him a hot-stone massage.’ She’s talking about the man with the red bobble hat and the dog. Someone I used to know. I’ve hired him before—that’s what she said. Finally, those words filter through. ‘Proud as punch, he was, when he told me that. Said it was a perk of the job—charged me for his treatment, cheeky sod.’

‘Stone,’ I repeat blankly.

Mary opens her mouth, says nothing. It hadn’t occurred to her.

Gemma Crowther, a healer. ‘Stephen was a chemist, a pharmacist, ’ I say. ‘She was a primary school teacher.’

‘Yeah, well, obviously they’d have had difficulty getting similar jobs after what they’d done. And not so much difficulty getting taken on by a garage, or some quack outfit like an alternative healing centre. Some places check out prospective employees’ backgrounds more diligently than others, presumably. ’ Mary throws her cigarette butt out of the window and rubs the small of her back with both hands.

‘Their new address—it was in Muswell Hill?’

She nods. ‘23b Ruskington Road. That’s where Aidan was going on Monday.’

‘But he didn’t know about . . .’

‘Yes, Ruth. He knew.’

Nothing will make me believe it. Aidan, seeing Stephen and Gemma behind my back? No.

‘When he turned on to Ruskington Road, Waterhouse overshot and carried on down the main road. By the time he’d realised his mistake and come back, Aidan had parked outside number 23. Right outside it, as if the space belonged to him. Waterhouse didn’t see me—and he was too busy concentrating on Aidan, who by this point was walking back to the main road. Neither of them saw me.’

‘Why?’ I blurt out. ‘Why would he park outside the house and then walk away?’

‘I’ve no idea,’ says Mary impatiently. ‘All I know is, Waterhouse followed him.’

‘Did you follow them?’

‘No. On foot, it was too risky. My hair’s hard to miss. Once they were gone, I went for a snoop. The bell for Gemma and Stephen’s flat had their names on it. Surnames only: Crowther and Elton, like the newspapers called them.’

Dong. Their doorbell at Cherub Cottage was called Dong.

Disgust warps Mary’s face. ‘Underneath the names, in tiny writing and in inverted commas, was the word “Woodmansterne”. ’

I clear my throat. ‘They lived on Woodmansterne Lane. In Lincolnshire. You mean . . .?’

‘If I had to guess, I’d say they decided to call their rented flat after their old street name.’

‘Yes. They’d do that. She would.’