Impossible, I want to say. ‘But . . .’ You’re too good for that to be true.

‘It’s true,’ says Mary. She kneels down in front of the dressing table mirror, lifts her chin and strokes her neck. ‘Aidan was the one who made me start painting. We . . . both of us were there, when she died. Neither of us saved her. Afterwards, we were both complete wrecks. We only had each other to talk to about what had happened. No one else would have understood. Aidan told me painting was what he’d always done to get rid of his pain. He didn’t say “pain”. He called it “all the shit that’s in my head”. There was shit in my head too, plenty of it, so I took his advice. He helped me, told me I was good, properly good. He said I was better than him.’

She breaks off. ‘There’s no excuse for the way I . . . forgave him everything he’d done to her. He told me what it had been like for him, and it sounded so different. Not at all like what Martha had told me. Even knowing how he’d treated her . . . As I said, there’s no excuse.’

‘Did you and Aidan . . .’

Mary snorts. ‘We became friends, nothing more. Or rather, I thought we were.’ She turns her head the other way, stares at her lined face, reflected. ‘So, now you see how selfish I am. I don’t hate Aidan for what he did to Martha. I like to tell myself I do, because it makes me feel better about myself, but it’s not true. I hate him for what he did to me.’

I haven’t got it in me to ask.

Mary rises to her feet. ‘Come on,’ she says. ‘I’ll show you.’

I follow her out of the bedroom. It’s less smoky on the landing, though some of the smell has drifted out. We go down the steep staircase into the large kitchen, through an open-plan lounge-cum-study with a beamed ceiling. This leads through to a narrow hall, at one end of which is a closed door. Mary reaches up for the key that’s balanced on top of the door frame. ‘I keep it locked,’ she says. ‘What’s inside is precious to me. No one’s seen it apart from Cecily, Aidan and the police.’

‘The police?’

‘The various unlucky members of the Farnham constabulary who come round periodically, when I get paranoid, to check Aidan isn’t hiding in the house with an axe. Except the one last night, he didn’t ask to look inside. They’re so sick of me by now, they don’t check properly any more.’