‘I don’t really mean 4D, I mean that the drugs aren’t drugs – as I said, the delivery system isn’t a chemical. It’s more like an infection in that it alters itself and its host, it evolves over time. The drug has a different effect after a month than after a day. You’ve seen that yourself. Your dream abilities are evolving.’

‘I suppose they are . . . I thought that was down to my effort, though.’

‘Chickens, darling. And eggs. The brain is a feedback system. Now. Try to follow my thinking. Meera is an engineer. They build things. If she and her team are messing around with certain kinds of devices, they may well discover something first and then figure out how it works later on. That’s what this sleepwalking study is about. They’ve found something that works and they want to see if they can legitimize it scientifically.’

‘OK . . . but it’s my client who’s sleepwalking, not me.’

‘You’re landscaping other people’s dreams.’

I smile. ‘Inception is my middle name.’

‘So, what if they’re working with something that impacts dreams and Bernard Zborowski has exposed you to it?’

‘Then I’m calling Scully for a check-up!’ I think I should get bonus points for working so hard to keep this convo lite. It’s never easy with O once she’s got her teeth into an idea. ‘But seriously, that would mean other people in the study might be suffering like I am. If you were looking for something to do, O, you could try tracking down those people and finding out if any of them have narcolepsy. Or if they can hack dreams.’

‘What makes you think I can do that?’ Her tone is so blithe that I stare at her for several seconds. I don’t know how to take her at all.

‘Nothing, O. Nothing makes me think you can do that.’

She wheels herself around to the plate-glass window and looks out over the rooftop. She has a big nose and a receding chin with a little white goat beard starting up, and the skin of her neck hangs like a wattle. She reminds me of a bird. She has given up too much information too quickly for my comfort. I wonder what else is going on in her head. She’s still chewing on something but she’ll never tell me what.

‘Go to bed,’ I say aloud. ‘You’ve had enough.’

‘I hate being in bed,’ O says. ‘I won’t be able to sleep. I’ll just lie there with my brain spinning.’

She gets like this sometimes. O is not cut out to be old, much less sick. She has this restlessness about her, a fierce focus. People are supposed to mellow with age, but if O can dial it back, I’ve never seen her do it.