Conway threw the phone back in her satchel, started circling again. The triumph had worn off fast. ‘That’s all Alison would give me, though. When I started asking about where Joanne got the phone, why she was selling it, Alison went whiny on me: “I don’t know I don’t know my arm hurts I feel dizzy can I have a drink of water?” That helium voice girls do, what the fuck is that? Do guys think that’s sexy?’

‘Never thought about it,’ I said. Conway was still moving. Something had her wound tight. I stayed back against the wall, out of her way. ‘Does nothing for me, anyway.’

‘Makes me want to punch them in the mouth. There’s nothing left on the phone from before last Christmas, no texts, no call logs: Joanne wiped it before she sold it. Here’s the good part, though. Alison didn’t swap her old SIM card into Joanne’s phone. When she bought it, her old one was out of credit, and Joanne’s one had twenty-odd quid left on it, so she just binned her old one and switched to using Joanne’s number. Which means we don’t need to track that number down, beg the network for the records, all that shit: we’ve got them already. Me and Costello pulled records on half the school, last year, including Alison. I rang Sophie; she’ll have them e-mailed to me any minute.’

‘Hang on,’ I said. ‘I thought you said none of the girls’ numbers linked up to Chris’s.’

‘They didn’t. But if Chris gave Joanne this phone’ – Conway gave her bag a slap, as she paced past – ‘to keep the relationship secret, that means he thought people might go through their normal phones. Right?’

‘Kids snoop.’

‘Kids, parents, teachers, whoever. People snoop. If Chris didn’t want that, and he was loaded, like Julia said? I guarantee he had a dedicated girlie-phone of his own. We go through the records off Joanne’s one’ – another slap to the bag, harder – ‘what’s the odds we find one number showing up for a couple of months before last Christmas, a shitload of contact back and forth?’

I said, ‘And then we check that number, Chris’s secret number, for links to the phone that texted me today. If he did this with one girl, chances are he did it with a few. If Selena actually was with him, she might have her own spare phone lying around.’

‘We cross-check Chris’s secret number for links to everyone. I knew, back last year, I knew it was weird he didn’t have his phone on him. These kids, they don’t take a shite without bringing their phones along. I should’ve— Jesus!’ A savage kick to Rebecca’s bedpost; it had to hurt, but Conway kept pacing circles like she felt nothing. ‘I should’ve fucking known.’