‘All our evidence says she hadn’t been in touch with Chris for weeks before he died.’

‘Right. Until you turn around and say, “Oops, actually, we’ve decided those texts were from her, not from you! Sorry!”’

‘Bit late for that,’ I said. ‘And we’ve had a lot of practice figuring out when people are lying. We both think Selena’s telling us the truth.’

‘Great. Glad to hear it.’

‘So if we believe her, why don’t you? She’s meant to be your mate; how come you think she’s a murderer?’

‘I don’t. I think she’s never done anything worse than talking during study period. OK?’

The defences shooting up in Julia’s voice, I’d heard those before. That was when it clicked: the interview in her room that afternoon, that note in her voice, something left snagged in my mind. I said, ‘You’re the one who texted me.’

Off Chris’s phone.

Her profile tightening. She didn’t look at me.

‘To tell me where Joanne kept the key to the connecting door. That was you.’

Nothing.

‘You said to us, this afternoon: When you found out about Joanne’s key, she turned it around on me. If anyone had told you about her and Chris, she’d have got back at them the same way. Meaning Joanne was getting back at you for telling us about the key.’

I got one corner of Julia’s eye. It said, Good catch. Now prove it.

Conway turned on the bench, pulled up one leg so she could face Julia straight on. ‘Listen. Selena’s in bad shape. You know that. You thought it was because she couldn’t handle being a killer, had to hide in cloud-cuckoo land. It’s not that. You want me to swear? I’ll swear on anything you want: it’s not.’

She said it clear and warm, the way she’d have said it to a friend, a best friend, to her closest sister. She was holding out a hand and beckoning Julia to cross that river. Go from the lifelong-familiar side where grown-ups were faceless mentallers trying to wreck everything, no point trying to understand them, over to this new strange place where we could talk face to face.

Julia looking at Conway. Things moving across her face said she knew the crossing was one-way. That you can never tell who’ll still be beside you, on the other side, and who’ll be left behind.

I kept quiet. This was theirs. I was outside.

Julia took a long breath. She said, ‘You’re sure. It wasn’t her.’

‘We don’t suspect her. You’ve got my word.’

‘Lenie’s not just naturally crazy, though. You don’t know her; I do. She wasn’t like this before Chris got killed.’