We were looking at each other in a way that made me feel magical. This wasn’t really friends. Izzy was my best friend. Joe made me feel that I was opening up, transforming into someone new. It was like staring into the sun. He lit me up and scared me. He was more than a human, more than a ghost. He was all the mysteries of the universe, the unknowability of life after death, a rip in the fabric of reality. But I was going to call it friends.

‘Best friends,’ he said. We stared into each other’s eyes and then I pulled myself together. He was at the same time a rip in the fabric of reality and an extremely good-looking boy.

‘Right,’ I said, trying to be brisk. ‘Updates time. I found Gus’s house. It’s one of those nice ones by the cricket pitch, like we thought. I waited outside yesterday morning. Sitting on a bench, pretending to play with my phone. And then he came out and went for a run.’

‘You saw Gus?’ Joe was stricken. ‘Was he … was he thirty-seven?’

‘Yes. It was so bizarre. I felt like a stalker, but I did this for you. When he was quite near, I pretended I was taking a selfie, and I took a picture of him instead.’

‘You pretended you were what?’

I picked up my phone and demonstrated. ‘Taking a selfie. Like this. Everyone does it.’ I showed him my phone. ‘See, there’s a camera this way too. Teenage girls are famous for taking selfies. Everyone thinks we’re very shallow.’ I pouted and held the phone up in front of us. We were both on the screen, but when I took the photo it was just me.

‘Oh my God,’ he said. ‘I’m not there. Look at that. I’m not even there.’ He turned and touched the wall behind him, which had appeared in the photo instead.

‘I bet that if you could take a photo I wouldn’t be in it.’

We stared at each other, eyes wide.

‘I can’t be in your photo because I don’t exist in your world,’ he said.

‘And I don’t exist in yours.’

‘I know it’s not the weirdest thing,’ he said, ‘but it is fucking freaky. I’ll bring a camera and we can try it. But!’ He shook himself. ‘Gus.’

‘Yes! OK. I pretended to be taking a picture of myself, but it was just so I could get a photo of Gus for you. I tried to make it look like I was using the camera that faced me, but really I was using the one that faced him. Right?’ Joe nodded. ‘Do you want to see it?’

He nodded again, and I knew that part of him really, really didn’t. I held the phone out.

‘Here,’ I said. ‘Here he is, on his Sunday-morning run.’