I noticed something odd about the bookshelves in the hallway. ‘These are out of order,’ I said. ‘The O’Brians are mixed up with the Penguins.’ Somebody must have taken them all out and then put them all back, hurriedly and out of order. No – it was simpler than that, I saw. ‘They took out a block of Penguins and a block of the O’Brians but put them back the wrong way round.’

I lifted out the mismatched block and found nothing. Neither was there anything behind the second block of books. Well, obviously there was nothing there because whoever had moved the books had taken what was behind them. But if they’d been in a hurry? I started stripping books on either side until I found something. It was a 5 cc disposable syringe, empty but with the cap seal broken. I removed the cap and sniffed the needle to find a faint medicinal smell. Used and discarded, then. I showed it proudly to Nightingale and Lesley.

‘She was a nurse,’ said Lesley. ‘It could be legitimate?’

‘Then why is it hidden in the gap behind the books?’ I asked. ‘It’s not very secure, so it must be something she needed to access in a hurry.’

‘They’re on the higher shelves,’ said Lesley. ‘Out of reach of someone in a wheelchair. So not for him.’

I sniffed it again, to no avail. ‘I wonder if it’s a sedative?’ I said. ‘Perhaps our Russian nurse was there to do more than look after him?’

I put the syringe back where I’d found it.

Lesley pointed down the corridor behind me where a couple of men and women in noddy suits were systematically pulling books off shelves and checking carefully for voids and hiding places.

‘You do know the search team would have found it,’ said Lesley.

‘It’s not good to become reliant on specialists,’ I said.

‘Hear hear,’ said Nightingale.

‘And we’re not specialists?’ asked Lesley.

‘We’re indispensable,’ I said. ‘That’s what we are.’

We had to wait while a couple more techs finished up in the living-room area before we could go in. Nightingale, despite being vacuum-packed in an earlier era, had taken to advances in forensic science like a man who knew a magic bullet when he saw one. He might be hazy about what DNA actually was, but he understood the concept of trace evidence and took everything else on trust.

Actually I tried to explain DNA fingerprinting to him once, but found I had to look most of it up myself. The biology I could understand. It was the various probability calculations that stuffed me – they always do. I’d have been a bad scientist.

Once the techs were out, Nightingale led us inside, making us aware of the circle of blue police tape surrounding a burnt patch on the carpet and the numbered tags scattered around the room.