Down the corridor outside, rattle of a trolley, clinking plates, warm smell of chicken and mushrooms making my mouth water. Someone – I pictured a frilly apron – was bringing dinner up to the fourth-years. McKenna wasn’t going to have them heading down to the canteen, spreading stories and panic like flu, yammering away with no nun to listen in. She was keeping them corralled nice and safe in their common room, everything under control.

Joanne’s phone records went blank till mid-January. Then a mix of other numbers, to and from, calls and texts. No sign of Chris’s number. Just what you’d expect off a girl’s normal phone; off Alison.

‘Sophie, you fucking star,’ Conway said. ‘We’ll get her on to the network, see if that number links to—’

I felt her go still. ‘Hang on a second. Two nine three—’ She snapped her fingers at me, staring at the screen. ‘Your phone. Show me that text.’

I pulled it up.

That triumph lifting Conway’s head again, making her profile into something off a statue. ‘Here we go. I knew I’d seen that number.’ She held out the two phones, side by side. ‘Have a look at this.’

That memory. She was right. The number that had told me where to find the key was the same number that had been playing phone footsie with Joanne.

‘Fuck me,’ I said. ‘Didn’t see that coming.’

‘Me neither.’

‘So either Joanne’s secret romance wasn’t with Chris at all, it was with one of our other seven—’

Conway shook her head. ‘Nah. A breakup would explain why the two gangs hate each other, yeah, but you can’t tell me we wouldn’t have got even one hint from somewhere. Gossip, or Joanne giving it loads of “So-and-so’s a big dyke, she tried to jump my sexy body,” trying to get the ex in shite. Nah.’

I said, ‘—or else someone just texted me off Chris Harper’s secret phone.’

A moment of silence.

Conway said, ‘Looks like it.’ Something in her voice, but I couldn’t tell whether it was exhilaration or anger, or smelling blood. Whether there was a difference, for her.

The day had changed again, shifted under our eyes into something new. We weren’t looking for a witness, in that roomful of shining hair and restless feet and watching eyes. We were looking for a killer.

‘The way I see it,’ I said, ‘there’s three ways that could’ve happened. One: Joanne killed Chris, took his phone, she used it to text us about the key because she wants to get caught—’

Conway snorted. ‘She does in her arse.’

‘Yeah, me neither. Two: the killer – Joanne or someone else – took the phone, handed it on to someone else.’

‘The same way Joanne sold her own to Alison. That’d fit her.’

‘Three,’ I said. ‘Someone else killed Chris, took the phone, has it still.’