She looks the way I am sick of feeling: at a loss.

Eventually she says, ‘Well, this is a new one. You’re saying that Aidan—how long has he been your boyfriend, by the way?’

‘Since last August.’

‘Okay. So pretty much since you started working for him?’

I nod.

‘Aidan believes he’s killed Mary Trelease, yet you know for a fact that she isn’t dead or even injured?’

‘That’s right.’ I flop back in my seat, grateful to be understood, finally.

Charlie Zailer’s eyes are narrow.

‘Forgive me if this seems like a stupid question, Ruth, but . . . have you told Aidan that Mary Trelease isn’t dead?’

‘Yes.’ I start to cry. I can’t help it. ‘I’ve told him over and over. I’ve told him until my throat’s sore and my voice is gone.’

‘And how does he respond?’

‘He shakes his head—he looks so certain. He says she can’t be alive, because he killed her.’

‘You’ve had this conversation many times?’

‘Hundreds. I’ve told him where she lives. He could go to her house and prove to himself that she’s still alive, but he won’t. He won’t go and see for himself, he won’t take my word for it—I’m getting desperate.’

Charlie Zailer taps her pen against the side of her face. ‘What you’re telling me is very odd, Ruth. Do you realise how odd it sounds?’

‘Of course I do! I’m not stupid.’

‘How do Aidan and Mary know each other?’

‘I . . . I don’t know.’

‘Brilliant,’ she mutters. ‘Are you sure Aidan isn’t having you on? He didn’t tell you on April Fool’s Day, did he?’ Seeing my expression, she straightens her face and says, ‘When did he tell you? Where were you, what was the situation? I’m sorry, Ruth, but this story is too way out for me.’

‘We were in London. It was last year, December the thirteenth. ’

‘Any particular reason you were in London that night?’

‘We . . . we went to an art fair.’

She nods. ‘Carry on.’

‘We were in our hotel. It was late. We’d been out for dinner and got back about half past ten. We went straight up to our room and . . . that’s when he told me.’

‘Out of the blue? With no warning, just, “Oh, by the way, I’ve murdered someone”?’

‘He didn’t say murdered. He said killed. And, no, it wasn’t out of the blue. Aidan was upset. He said he didn’t think our relationship was going to work unless we . . . unless he confided in me, but he obviously didn’t want to. I could tell he was dreading it. I was too.’

‘Why?’ Charlie Zailer leans forward. ‘Most people don’t dread being confided in by their partners. Most women, especially, would be gagging to know. Did you have reason to believe Aidan might have committed a violent crime?’

‘No, I . . . no. None.’ Most women. She is talking about people for whom the word ‘secret’ means a tantalising prospect, not a source of anguish.