We passed a heavy-looking door with a panel of wire-strengthened glass. It gave access to a corridor into the left-hand wing of the house. Next to it a security guard sat filling in some forms. The security was obviously tight, but still a thought arose: if Rachel had once been detained here, if her mind was unstable, could Lorelei have died under her hand?

We climbed a wide oak staircase scored with deep welts and approached a door of intricately carved wood, upon which the orderly thumped with his fist. From somewhere behind it, a voice told us to enter and we did so to find a short man in his shirtsleeves peering at us from behind a glass desk. ‘Good evening,’ he said. ‘I’m Dr Larren. I’m sorry I said I was busy, but there’s a lot to do right now. If I can help you, I will. You said something about a car?’

Tibbot showed him his warrant card. There was no use hiding it now. ‘You were given a car two years ago. Well, you took one, anyhow.’

‘I’m sorry, but no. No, I didn’t.’

‘Police records say you received a Sunbeam. Registration YXA 998.’

‘I don’t know what to tell you, Detective Sergeant, that’s not my car.’ He poured a glass of water and drank.

‘We’re trying to find the woman who owned it before you. Her name is Rachel Burton. Is she a patient?’

‘No. We don’t have any patient by that name.’

‘You’re certain?’ Tibbot asked.

‘Yes. We have fewer than forty patients. I know them all personally. I make a point of it. Only eight or nine have arrived in the past few years and she isn’t one of them.’

‘Could she have been here for a short time?’

‘Even then I would have known her.’

‘This is a most important enquiry.’

‘I’m sure it is, but I can’t help you.’

‘Could you ask your staff?’

He looked amused. ‘I’m afraid they would tell you the same thing.’

‘You can’t be certain of that.’

‘But I can, officer.’

‘Dr Larren …’

It was ridiculous and I could see no point going on with it. The man wasn’t going to tell us anything. ‘Look,’ I said to Tibbot. ‘Let’s leave this and just go. Please.’

Tibbot seemed frustrated. He checked his notebook, although it must only have been to give him a chance to gather his thoughts. ‘All right,’ he said. ‘The registration records must be a mistake. Thank you for your time.’

‘I’m sorry I couldn’t be of help.’ Larren picked up a pen and returned to some papers on his desk.

Tibbot followed me out of the room and we were met by the orderly, who was waiting to escort us out of the building. As we went, I noticed how thin the staircase carpet was – little more than threads.