‘It means I’m going home to Essex tomorrow,’ she said. ‘Also, I know you have a strange disregard for basic procedure, but Nightingale is the SIO on the Little Crocodiles case and Seawoll is SIO on the James Gallagher murder. Meaning that you need to talk to at least one of those before you do anything. Including getting out of bed.’

‘At least bring me my laptop,’ I said.

‘Fine,’ said Lesley.

‘And some grapes,’ I said. ‘I can’t believe I’ve been in hospital overnight and nobody brought me any grapes.’

After Lesley had buggered off, I checked in the waste-paper basket and found not one but two flimsy plastic containers with denuded grape stems in them. I then spent a happy half an hour plotting a series of increasingly bizarre revenge pranks on Lesley before Nightingale arrived with a change of clothes. This being Nightingale, he’d brought my fitted M&S navy suit that was, strictly speaking, reserved for funerals and court appearances.

I told him my theories about the Faceless Man and Crossrail and it started sounding thinner the longer I talked. But Nightingale thought it was worth checking out.

‘At the very least,’ he said, ‘we need to eliminate the possibility.’

We were interrupted by a surprisingly young registrar with stumpy brown fingers and a Brummie accent who took my blood pressure and another blood sample. I asked after Dr Walid and was told that, since I wasn’t in any danger, he’d left for Scotland the night before.

‘Amazingly undamaged,’ said the registrar. ‘But he wants you to stay overnight for observation. You’re suffering from exposure so you need to rest, take on fluids and stay warm.’

I told him that I had no intention of getting out of bed and he wandered off, content. Nightingale said I did look tired and that he was going to leave me alone to get some sleep. When I complained I was bored he left me his copy of the Daily Telegraph and suggested that I try the crossword. He was right – fifteen minutes later I slapped it down on the bed.

‘Twelve down,’ said Tyburn. ‘To owe much to others – six letters.’

She was standing in the doorway wearing brown slacks and a snowy-white lamb’s-wool rollneck jumper.

‘Aren’t you going to wait for me to recover before calling it in?’ I asked.

She entered and sat primly on the end of my bed and looked around the room – frowning.

‘Why haven’t you got any grapes?’ she asked.

‘I’ve been asking myself the same question,’ I said. ‘You didn’t bring flowers, either.’

‘Do you think there’s people living in the sewer system?’ she asked.

‘Do you?’ I asked.

‘I think it’s a possibility,’ she said. ‘And if it’s true it’s an issue that will have to be addressed carefully.’

‘And you think you’re just the woman for the job?’