‘OK,’ I said. ‘OK. This is weird. You’re not the only … person like you. That I see. I hate it when I see the other ones. They don’t see me. They don’t notice me at all. They walk right through me. I don’t hate seeing you.’

‘Thanks,’ he said. ‘I’ll take that.’

‘I mean, you can hear me and you seem like a … like a real boy.’

‘Like Pinocchio,’ he said. ‘Are you serious, though? 2019?’

I watched his face. Now that we’d stopped laughing, he was looking very confused indeed.

Meeting Joe changed everything. It gave me hope. It made me see that, in this strange universe, I might be able to see Mum again one day. It went through me like lightning. Everything changed. Perhaps I would talk to her like I was talking to him. This was everything in the world that I wanted becoming possible.

Anna Brown, I said in my head as I watched Joe working out what being from the past actually implied. Anna Brown, come to me. Mum. Please. Mum. I need you. I thought of Mum, and the colour blue, as hard as I could.

‘I can’t be a ghost,’ he said. ‘I’m not dead. I’d know if I was dead, wouldn’t I?’

Joe and I went to the same school. Sometime before Sasha started there, Beachview Secondary had become the South East Devon Learning Academy, known to everyone as Sedla, which was widely agreed to be a stupid name for a school.

We talked about details, but the magic of it all pulsed through me. It was magic. Ghosts were real. Even if Joe was alive somewhere in 2019, I was talking to his past self right now, and so it was possible to communicate with someone from the past and that meant I could talk to Mum again.

I didn’t want to leave this room. I had found Joe, a link to 1999, and I never wanted to stop talking to him. I wanted him to tell me everything about what it was like to be him, and whether he knew other ghosts, but I knew he wasn’t ready to do that, so we talked about easier things at first.

In Joe’s world it was 1999, and he was about to go on a French exchange trip. In my world it was 2019 and Mum had been dead for a year tomorrow. In his world she was alive, but I was nearly four years away from being born. Sasha was in his world as a baby. She could have been one of the kids Joe’s dad looked after. Had she gone to a nursery called Bouncers? I would find out.

‘What happens next year?’ Joe said. ‘Do the computers stop working in the year 2000? Because that’s what they’re saying.’