‘No,’ I said. ‘I explained to you. The knives were identical.’ Then I remembered. ‘Actually, there was one thing. My dagger had a sort of decoration on the hilt. A round disc. It was loose.’

Cara raised her eyebrows as if to say that this was what she had been expecting. ‘And where is your dagger?’ she asked.

I was ahead of her. From the moment she’d mentioned the dagger, I’d been wondering what I’d done with the bloody thing. I remembered opening the package at the stage door and talking about it with Sky Palmer. I’d certainly had it with me when I went into the green room. But after that, things were a bit hazier. I’d had a lot to drink, both at the formal cast party and afterwards. Then there had been the bombshell of the review and the whole evening had disintegrated. All I’d wanted to do was go home. I was sure, though, that I’d brought it with me. I could see it in my hand as I walked the short distance up the Strand and across to Clerkenwell. What could I have done with it when I got in? I tried to reconstruct my movements. I hadn’t wanted to disturb Jill, so I’d used the downstairs bathroom. I’d left my clothes on the piano.

But I had gone – briefly – into my office on the top floor! I remembered that now. I’d wanted to check my emails to see if any of my friends had said anything nice about the play. And I’d put the dagger on my desk beside the computer. I must have done.

‘It’s upstairs,’ I said.

‘Would you mind getting it for us?’

‘Not at all. I’ll just be a minute.’

I didn’t like leaving them there. I didn’t want them going through my things. But I had to get this over with and so I ran up to my office, which was right at the top of the flat, and went straight to the computer. And the knife, of course, wasn’t there.

It’s been the same ever since I turned fifty. I spend hours every day looking for glasses, my wallet, my phone, the letter I need, the shopping list I’ve been given. I hate the idea of getting old, but that’s how I feel when I go into a room to get something and forget what it is I’ve come for before I can even begin looking. And then there are the false memories. The pen that I definitely put in my pocket. The watch that I’m sure I left by the bath. Except I didn’t – and they’re not there. That was how it was now. I quickly searched my office but I knew that I wouldn’t find the dagger. It seemed likely that I’d never brought it home in the first place.

I went back down.

‘It’s not there,’ I said, trying to sound casual. ‘I must have left it in the theatre.’

‘We’ve been to the theatre,’ Cara said, barely able to keep the triumph out of her voice. ‘It wasn’t there.’