‘We all call him Bill.’ And it had never occurred to me to ask why, why he felt he couldn’t use his real name with us, his closest friends.

‘Alison. We’ve had you in because I understand you’re close friends with one of the boys we’re looking at, Michael Morris.’

‘That’s right. We’re all friends.’ I rubbed my hands together; they felt clammy.

‘And you and Michael are . . . together? Dating?’

It seemed very important I play this down; I didn’t know why. ‘Oh, not really. Now and again. Friends really.’

‘So he wouldn’t have minded you being off with Bilal.’ This was the woman who spoke. It had never occurred to me that Mike would mind anything I did, but I suddenly wondered. Had he been angry, when he saw I was gone? Had he drunk more than usual?

‘We’re all friends,’ I repeated.

‘When did you last see Michael, before you left?’

I screwed up my eyes. ‘I think he was on the lawn. Getting a drink. A whole bunch of people were there but I just wanted to see the sun come up.’

‘You’re sure you saw him?’

‘Yes, I’m sure.’ And I was sure. We’d had a row, even. I just wasn’t sure what time it was.

‘When was this, Alison?’

‘I’m not sure. Maybe an hour before we got back and the college was shut down.’

They exchanged glances. ‘Bilal seemed to think it was longer.’

‘I don’t think it was that long. It was almost light already.’ Was that right? I told myself it was, probably. That I wasn’t even lying.

They exchanged a look. My stomach sank. But really, how could they prove me wrong? I’d just said I thought it. Anyone was allowed to think something. I pushed down the thought of Martha, how beautiful she’d been in her white silk. Her hand, bruised and limp. ‘Did you know Martha well?’

Safer ground. I felt it like when your feet catch the bottom again in the sea. ‘Not really. She was nice. But we weren’t friends.’ I bit my lip. ‘It’s so awful. She was so lovely.’

‘Ali, did you ever see any of your friends take drugs?’

‘God no, we don’t do that. I’ve never touched them.’ That at least was true. Were drugs involved? Had Martha been given something, the thing we were warned about? Don’t leave your drink unattended. Don’t accept drinks from strangers. But there were no strangers at the ball.

Except the one who had somehow scaled the ten-foot wall and killed her. ‘Did she – is that what—’ A drug overdose was sad, but no one’s fault. A chink of light opened up to me. Maybe no one did this after all. Maybe I wasn’t doing a terrible thing.

The man detective looked at me. ‘Martha was strangled, Alison.’