I felt a sudden desire to talk to Sam, to ask him some questions, but surely a five-year-old wouldn’t remember whether his father or mother had looked after him on a night days ago. And there was another question I needed answered, too, before he made me leave.

‘Wait, Alex – why didn’t you tell me? When I told you what had happened to me, going to prison. Why didn’t you say the same thing happened to you? With Stacey?’ If anyone could have understood him, it was me.

He sighed again. ‘Oh, I don’t know, Rachel. I try not to think about it. It was a bad time in my life, all right? I tried to do the right thing and walk her home – we were friends from school, and she was hammered, but she wouldn’t let me take her to the door in case her parents saw. Next morning I’m in bed hungover and the police are at the door. Everyone at the party said I was the last one seen with her. Then it’s like – this nightmare you somehow can’t wake up from. Trying to prove you didn’t do it when there’s no evidence either way. I was terrified – I was barely eighteen, and I thought I’d go to prison for life.’

‘I know,’ I said quietly. ‘If anyone knows, it’s me.’

‘So. Everyone round here knows about it, and I’m sure a good few still think I did it. Her family moved away.’

‘You didn’t want to leave too?’

He shrugged. ‘Why should I? My family have been here for generations. Our home’s here; I wasn’t giving that up. Anyway, it’s just gossip. It can’t hurt me.’

I wished I could take that view. My mind was working overtime. ‘You don’t think – maybe someone thinks you did it back then, and wants to pin Anna’s murder on you? To frame you? I know it sounds mad.’

He looked at me curiously. ‘Why would someone do a thing like that? And anyway, the evidence doesn’t point to me, does it?’

He was right. The evidence so far all pointed to me.

I walked down the stairs of Alex’s flat, feeling jittery and afraid. Even if I was sure Alex had lied to me – and I wasn’t – I would never be able to prove he’d been at Anna’s house that night. Would I tell the police on him, assuming they didn’t already know what Don had told me? A murder enquiry is certainly a sobering way to evaluate how much you care about someone.

Rounding the staircase to the middle landing, I almost fell over Sam, playing with some cars on the steps, making little whirring racetrack noises. He looked up – he was wearing an Octonauts T-shirt and jeans, his cheeks flushed.

‘Oh! Hello,’ I said.