I looked at my watch. It was already eleven o’clock. I’d been twiddling my thumbs all morning, but finally I could see a way out of this nightmare. Unless the superintendent was as mad as they were, he or she would understand that I was completely blameless and that Cara Grunshaw was pursuing a personal vendetta. Apart from the murder weapon, there was no evidence whatsoever to implicate me. Ahmet had handed out at least five of those absurd, cheaply made daggers, and for all I knew, he could have a dozen more at home. And did she really think I would murder Harriet Throsby simply because she had given me a bad review? It’s critics who kill writers, never the other way round.

‘I’m fine, thank you,’ I said.

It might have given Cara some measure of satisfaction, leaving me here the whole morning. But I could put up with it because I was counting the hours before I walked out of here. I was sure of it. I would get a taxi home. I would have a bath and put all this behind me.

So why was Mills still smiling?

Cara Grunshaw produced a sealed bag. Inside it I saw one of the Macbeth knives, coated in blood that had turned brown and smeared itself across the plastic. Seeing it like this only reminded me what an absurd gift it had been in the first place. It wasn’t even as though it was simply an ornament. It was actually lethal!

‘This is the dagger that killed Harriet Throsby,’ Cara said. ‘It’s your dagger. We have examined all the others and this is the only one that has a faulty design. More to the point, your dagger is the only one that’s unaccounted for. How do you explain that?’

‘I left it in the green room,’ I said. ‘Anyone could have picked it up.’

‘You told us you took it home,’ Mills remarked, with evident satisfaction.

‘I thought I had. I must have made a mistake.’

‘You lied to us.’

‘No. It was a mistake.’

‘We found a set of fingerprints on this dagger,’ Cara told me. She was holding the bag in front of her as if she could actually see them. ‘They are your fingerprints, Anthony. They’re a perfect match.’

‘I held the dagger when I was at the Vaudeville. I’m not denying that.’

‘And you’re saying someone stole it. But there are no other fingerprints on the hilt, which means that they would have had to handle it very carefully. Do you think they were deliberately trying to incriminate you?’

‘I suppose that’s possible.’

‘Payback for writing such a crap play,’ Mills sneered.

‘Do you know where Harriet Throsby lived?’ Grunshaw asked.

I sighed. ‘Yes. Twenty-seven Palgrove Gardens, Little Venice.’

Her eyes widened at this admission. ‘How did you know that?’ she demanded.

‘You told me when you arrested me.’

Cara thought back. I saw the calculation in her eyes. ‘I didn’t mention Little Venice.’

‘You said W9. Anyway, I know where Palgrove Gardens is. I often walk my dog along the Regent’s Canal and it’s close to the tunnel.’