“Doesn’t matter.” They’ll believe I’m a trainee if I tell them to: that’s the beauty of the card, it’s official ID with a class four geas attached, and as long as I’m using it on official business it will draw on the full authority of the organization to convince anyone I present it to that I’m on, shall we say, whatever official business it is in the best interests of the organization for them to believe I’m engaged in. The only people it won’t fool are other Laundry staff and seriously powerful sorcerers. I don’t like using it on civilians, but it’s less hassle than calling the ops room to yell at her boss, and more merciful than the other options I have up my sleeve. “I need to see Sara’s route. This is official police business.”

“I’ll take you there. (Never heard such a thing . . .)” She leads off, muttering to herself and periodically glancing back at me with angry-eyed suspicion, clearly disturbed by the impact my lack of office cleaning chops is going to have on her workload.

I follow Eva into the maze of twisty little corridors and open-plan cubicle areas that comprise the back-office IT support section of the bank. There are no windows—we’re below ground level here—but there’s an omnipresent dull roar of air conditioning that paradoxically makes everything sound muted: I guess it swamps other noises. Most of the offices are relatively spartan and cheaply furnished. Employees with the status to rate a window view don’t generally work down here. And it’s largely deserted. The market’s closing bell has long since rung, and most of the staff have long since gone home or buggered off to the wine bar. With a sinking feeling I begin to wonder if I’ve left it too late—if the brain-eating phantasm I’m searching for comes and goes with the day shift. I have a smartphone loaded with our OFCUT suite and a suitably bluetoothy sensor, and I periodically check to see if it’s picked up anything: but no, there’s not so much as a haunted print server down here, much less a nest of don’t-be-silly-Bob.

Eva leads me past a familiar-looking door that screams server room at me. It’s secured by a keypad, with warning notices and a breeze blowing from around it. I spot a prominent red handle under a perspex cover, beside a notice warning of the risk of asphyxiation in event of a halon dump. I pause and check my OFCUT readout again. There’s a very faint yellow warning, barely budging the needle: but that’s enough to get my attention. “Why are you dawdling?” demands Eva, glaring at me. “We’ve got offices to clean!”