Behind her shoulder, Conway’s eyes said Careful. I shrugged. ‘We can’t say that yet. I’d just like to know if anyone had the opportunity.’

Julia thought. Shook her head, reluctantly. ‘I don’t think so. I mean, obviously I’d love to say yeah, but actually there’s not a chance in hell anyone would’ve got up there without a really good excuse. And even then, no way would she have been allowed on her own. Seriously, when I asked could I go get my French homework, Houlihan acted like I’d asked to go into a drug den and buy heroin.’

The violin under Rebecca’s bed. The flute in Selena’s bit of wardrobe. I said, ‘What about during activities? Anyone go missing then?’

‘Seriously? You think I’d’ve noticed? If you’d seen the mess the place was in . . . Plus I was concentrating on trying to get that phone. Joanne and Orla do drama too, and I know they were both there because Joanne kept trying to burst into tears’ – Julia mimed puking – ‘and Orla had to comfort her and shit. But they’re the only ones I remember.’

‘We’ll try asking your mates.’ I said it nice and casual. The moonlight blazed into my face, felt like it was stripping me naked. I tried not to turn away. ‘Do they do drama as well, yeah? Or would they be able to tell us about other groups?’

‘We’re not actually surgically attached. Holly does dance. Selena and Becca do instrument practice.’

So they would have had to go back to their room to get their instruments. Two of them together, to protect each other from the brain-eating maniac; they would have been allowed.

‘Right,’ I said. ‘How many people in those, do you know?’

Julia shrugged. ‘Lots of people do dance. Like forty? Instruments, maybe like a dozen.’

The odds said the rest had been day girls. We would check the logbook, but if the numbers held, Rebecca and Selena had been the only ones through that door.

The sudden quiet, all the day’s jabbering and wailing fizzled away into that white silence. Rebecca holding out the phone she had taken to make sure that Selena was safe, that no one could ever link her to Chris. Holding it out like a gift, priceless. Like salvation.

Or: Selena burrowing in the wardrobe for her flute, slow with shock and grief. Behind her back, Rebecca, light as a ghost and just as urgent, leaning over her bed. Selena was the one who had started keeping secrets. She was the one who had let Chris in, to start things cracking apart. It had been her fault.

I looked at Conway, across that lone gallant slash of red. She was looking at me.

‘Right,’ I said. ‘Your mates might remember someone leaving. Worth a shot, anyway.’