I’m not safe, but it’s good enough for now. After I cleaned my pee off the floor, I took out the earring. Now, two cups of espresso later, I feel awake enough to slice potatoes and put on some onions to make a Spanish omelette. At dawn I bring O her Ada Lovelace mug in bed. She’s already awake, as usual.

‘Stay,’ she says. ‘Sit down.’

I perch on the end of the bed. Grey light is floating into O’s bedroom through a bank of windows that look out the park across the road. There are bookshelves on two of the three other walls; the wall above the bed has a single small painting by Préfète Duffaut. Pink roads lead over bridges and into mountain landscapes that cut across one another in a way that defies three dimensions. It’s as if someone chopped up an archipelago and sewed the bits back together skew-whiff. The landscape is bright and happy, not bothered by its own confusion.

I used to be like that. Lately, not so much.

‘You had a bad night?’

I tell her a little about it. Not every detail. It’s too whacky, and it’s hard to talk about without sounding unhinged. Besides, we have more important things to discuss.

‘This Dream City that figures in recent matters,’ O says finally. ‘Melodie wandered into it, and you’ve mentioned that it’s never happened with a client before. What do you think the Dream City really is?’

The question is typical O. She’s always looking for the big picture.

‘Well, at first I thought it was a part of me. It’s been the setting for my dreams for months now. I’d see these people in greyscale with masks, and I thought they represented my anxieties about trying to help clients. Because I never seem to be able to help anyone.’

‘And it’s been going on since you fell ill.’

‘Yes . . . well, the odd thing is that when you’re there, you feel as if you’ve always been there and always will be. I can’t say with any certainty when I became aware that I was returning to the same city night after night.’

‘But Mel did tell you that she’d been in the Dream City on her own?’

‘Yes, she did.’

‘So the Dream City isn’t necessarily exclusive to you.’

‘No, I don’t see how it can be. I’m starting to think the sleepers are other people using Sweet Dreams. You know, I can see them but I don’t think they can see me. They act like they don’t know where they are.’

‘And you believe that Mel was tricked into walking off the rooftop.’

I’m shivering as I nod. ‘It nearly happened to me, last night. The dreams are so real, so vivid.’