‘So this is where I am with it,’ he says eventually. ‘But there are so many unanswered questions. Especially: how could the dreamhacker learn to do that to someone? It’s easy enough to see why they’d want to do it. All kinds of perfect crimes would become possible if you could refine the method.’

I hate this. My dreamhacking is intended to help people improve their lives in nice, happy ways – stop smoking or drop ten pounds or resolve their childhood phobia of poodles. None of this is what I signed up for. I want to run far, far away.

Roman says, ‘I’ve been tracking sleep crimes for a few years now and I think we’re seeing the learning curve of one or more dreamhackers reflected in the increasing sleep-related deaths around Greater London. This is one reason why we wanted to talk to you. Because you’re not the first dreamhacker, but your abilities are developing. You can do more than others who received the treatment at the same time. Maybe you’re close to being able to make people sleepwalk, too.’

‘What others?’ I say sharply.

‘Sorry?’

He didn’t mean to say that. He’s put his foot in it now. He can’t look at me. I asked O to find the other trial participants but she never came back to me. If only I could meet my own kind . . .

‘I repeat: what others, Roman? If you want my cooperation, you need to level with me. Who else are you talking to? How did you find them?’

‘I’m not allowed to tell you. For your own protection and theirs, and for mine, if I’m honest. I’m sorry, Charlie.’

‘Yeah, you’re sorry.’ That’s code for: we suspect you. Who wouldn’t? Stupid damn tears are welling in my eyes now. Roman doesn’t understand. There are other people who have the same problem as me! He knows them and won’t tell me who they are. They could be my enemies but they could also be my friends. I’ve been trying to figure this all out in isolation and maybe that’s not necessary. I want to meet my people!

‘I don’t want you to think that I think you’ve done anything wrong, Charlie.’ He touches my arm gently. ‘If I did, I’d never speak to you off the record like this. I wouldn’t . . . I wouldn’t return your bras or ask if you’re OK or lie awake worrying about you— I mean, you know. All in the line of duty.’

‘They’re not my bras, by the way,’ I say quickly.

He flushes pink. I pretend not to notice.