‘Which house is number 27?’ Hawthorne asked.

‘I don’t know …’ We continued on our way until, suddenly, it occurred to me. ‘You asked me that on purpose!’ I exclaimed.

He looked at me innocently.

‘Yes, you did. You wanted to know if I’d already been to her house. Do you really think I’m stupid enough to fall for that?’

‘Well …’

‘And you’re still ready to believe I could have killed her!’

‘I’m trying to keep an open mind.’

I pointed. ‘There it is, over there. I may be wrong, but I’d guess it’s the one with the policeman standing outside.’

The taxi drew in. We got out, I paid and then together we walked up to the front door. There were two bells. Hawthorne rang the lower one – marked Throsby. I thought the policeman might stop us from entering, but he had barely acknowledged us as we approached. Maybe Hawthorne had a certain authority about him. After all, he had visited enough crime scenes.

Arthur Throsby opened the door.

It had to be him. He had the blank, exhausted look of someone whose life has been turned upside down. We were two more strangers entering his house to ask yet more questions and he looked at us with sad resignation.

‘Yes?’ he asked, incuriously.

‘Mr Throsby?’

‘I’m Arthur Throsby, yes.’

‘My name is Daniel Hawthorne. I’m very sorry for your loss. I’m helping the police with their inquiries. Can we come in?’

Hawthorne was lying. In fact, he had lied twice. He wasn’t officially helping anyone except me. And he wasn’t sorry at all.

Throsby looked puzzled. ‘I’ve already spoken to Detective Inspector Grunshaw,’ he said. ‘I’ve made a full statement.’

‘Yes. There were a couple of things she wanted to follow up on.’

‘I thought we’d covered everything. She didn’t say anyone else would be coming.’

‘Mr Throsby, we’re trying to find out who killed Harriet. You can phone DI Grunshaw if you like. But I think it’s fair to say that every minute we waste is a minute the trail gets cold. It’s up to you.’

He was bluffing, of course, but it worked.

‘No. It’s all right. I’m … well, I’m sure you understand.’ Throsby stepped back to allow us in. This was something I’d learned after three investigations with Hawthorne. When someone was murdered, people expected to be asked questions. It was as if they’d seen so many murder stories on television, they knew the part they had to play and didn’t ask too many questions themselves.

We stepped through the front door and found ourselves in a narrow communal area with two further doors facing each other at angles. Harriet Throsby had lived with her husband and daughter in the ground-floor and basement of the building, with access to the garden, while a second flat had been carved out above. The door on the right was open, showing a brightly lit, airy space with a wide corridor leading into an open-plan kitchen and living room with French windows at the end. The taste was simple, on the edge of chintzy: floral wallpaper, lots of brightly coloured vases and original theatre posters hanging in frames. The wooden floor, what I could see of it, was original, but we were standing in an area that had been covered by translucent plastic sheeting with numbered tags underneath.