Before she left, she walked round the flat taking photos with her phone: the rumpled bed, the kitchen, which was full of empty wine bottles, the sink piled high with washing-up, even the bathroom.

‘What are you doing?’ I asked.

‘You’re going to think I’m a real sap, but I want to be able to picture you here when I’m not with you.’

‘What, among all the mess?’

She put her arm around me and held the phone up to take a snap of us together.

‘Say sausages.’

She took the snap then told me she needed the loo before she went. I sat and flicked through the newspaper, becoming absorbed in the latest news about the Dark Angel serial killer who had been found guilty of the murder of twenty-three elderly people. There was a photo of the guy who had discovered what she’d done, a former neighbour of hers. He said he hoped she would rot in jail and then burn in hell. Not for the first time, I was glad my neighbours were agreeable.

Charlie came back into the room, smelling of perfume. For a moment, she was caught in the sunlight coming through the window.

‘Why are you looking at me like that?’ she asked.

‘Just . . . because.’ I stood up and pulled her close to me, peering into her eyes, pretending to examine her. ‘Are you real?’

She squirmed away. ‘What do you mean, you idiot?’

‘You seem too good to be true.’

I had expected her to treat what I was saying jokily but she was surprisingly serious. ‘I’m really not that good.’

Apart from some of the more intense moments in bed, most of our exchanges over the past week had been light-hearted and playful. This new gravity took me aback.

‘I was only messing around,’ I said and, after staring at the carpet thoughtfully for a few long seconds, she finally smiled.

‘I just want you to know that—’ she began. ‘Oh, this is crazy.’

I took her hands. ‘What is?’

‘Nothing. I’m being stupid, that’s all. Ignore me. I’m about to start my period and it’s making me feel a bit girly and emotional. Please stop me before I say something I regret.’

We hugged and I didn’t want to let her go. But Sasha needed me, and it was time I stopped being such a bad friend.

As I was about to leave, my doorbell rang. It was Kristi, my cleaner.

‘I completely forgot you were coming,’ I said.