‘Do we know why he was singled out?’ asked Seawoll.

‘No,’ said Nightingale. ‘Although all the cases seem to start with a sense of grievance. Coopertown was bitten by someone’s pet, Shampwell was struck by a motor vehicle while riding.’

Seawoll glanced at Stephanopoulos. ‘Hit and run on the Strand, sir, in a CCTV blind spot.’

‘A blind spot?’ asked Seawoll. ‘On the Strand?’

‘Thousand-to-one chance,’ said Stephanopoulos.

‘May,’ barked Seawoll, without turning round. ‘You think there are related cases?’

‘Including the incident Grant and I witnessed in the cinema, and the one that took place just prior to Shampwell’s death, I’ve identified fifteen cases where the perpetrators have shown uncharacteristic levels of aggression,’ said Lesley. ‘All people with clean records, no psychiatric history and all within half a mile of Cambridge Circus.’

‘How many do we know were actually’ – Seawoll paused – ‘possessed?’

‘Just the ones whose faces fell off,’ said Nightingale.

‘Just so we’re clear,’ said Seawoll. ‘The Commissioner wants this kept quiet, so PC May liaises with PC Grant for the low-level stuff but anything significant, anything at all, you talk to me. Do you have a problem with this, Thomas?’

‘Not at all, Alexander,’ said Nightingale. ‘It all seems eminently sensible.’

‘His parents are flying in tomorrow,’ said Dr Walid. ‘Is it all right if I sew his face back together?’

Seawoll glared at the body. ‘Fuck,’ he said.

Nightingale was silent on the drive back to the Folly, but at the foot of the stairs he turned to me and told me to get a good night’s sleep. I asked him what he was going to do, and he said he’d work on some research in the library – see if he couldn’t narrow down what was doing the killing. I asked if I could help.

‘Train harder,’ he said. ‘Learn faster.’

As I went upstairs, I met Molly gliding down. She paused and gave me an inquiring look.

‘How should I know?’ I said. ‘You know him better than I do.’

You don’t tell your governor that you need a broadband connection, cable for preference, because you want to watch football. You tell him that you need the internet so you can access HOLMES directly instead of having constantly to rely on Lesley May. The football coverage, movies on demand and multiplayer console games are all merely serendipitous extras.

‘Would this involve physically running a cable into the Folly?’ asked Nightingale when I tackled him during practice in the lab.

‘That’s why they call it cable,’ I said.

‘Left hand,’ said Nightingale, and I dutifully produced a werelight with my left hand.

‘Sustain it,’ said Nightingale. ‘We can’t have anything physically entering the building.’

I’d got to the point where I could talk while sustaining a werelight, although it was a strain to make it look as casual as I did. ‘Why not?’