‘“Longbarrow”,’ said Ross. ‘That limits what he was dreaming about to a set of specific places. Maybe he was trying to tell us where to find the Ripper.’

‘With fingerprints on the wall,’ said Costain. ‘So that’s something we can follow up on. I’ll bet there are records of fingerprints found at prehistoric sites. We find out where that longbarrow he mentions is; if it’s real, at least we can go and see it, maybe find out why it’s relevant.’ He did an image search on his phone for barrows with handprints and showed them three pages of results. ‘Doesn’t really narrow it down,’ he said. ‘Six of these are in London, and four of them are now buried under shopping centres and stuff like that.’

‘Send the pictures of those prints to Forensics,’ said Lofthouse, ‘they’ve got databases of fingerprints going back centuries, maybe some connection will leap out at us.’

Ross did as she asked.

‘I really want to go to sleep,’ said Sefton. ‘I should think you lot do and all. But now I know what Jimmy knew. Now we all do. If that’s what got him killed…’

Lofthouse nodded. ‘This better be on my head,’ she said. ‘I’m ordering you all to take the meth.’

Sefton found himself desperately wanting to say no. As an undercover, he’d always turned down drugs, plus he wasn’t sure if his system could stand it. But what was the alternative?

Costain got out his packets and looked to Ross with a raised eyebrow. ‘Orders are orders,’ he said. She just looked coldly back at him.

They all sniffed the powder. Sefton erupted into a coughing fit and hated the sharp feel of it up his nose. But after a moment … yes, it did make him feel better.

Lofthouse didn’t partake. ‘So,’ she said, ‘James said your next move should be to raid the Keel shop?’

Costain nodded, a bit too quickly. ‘Yeah. Okay. Okay. We can interview Keel about scrying glasses: if he’s got one; who else does he know who has; if there’s any defence against them.’ He gestured to the mirror that stood outside the window. ‘We can ask what that thing is – if it’s just a fake that Vincent got stuck with, which just happened to have the Ripper come out of it—’

‘Or whether the object itself was actually a trap,’ said Lofthouse, ‘using the Ripper, maybe set up by those “dark forces” Vincent thought were working against him. Either way, you might get a lead on who was trying to kill Vincent, why that was so long before the other attacks, and why, uniquely, that one failed. And we might find some way to protect you three.’

‘The strike starts at noon tomorrow,’ said Costain, looking interrogatively at her. ‘Noon. Tomorrow. Do we do this off the books? Do we even have time to do it any other way?’