The atrium looked largely as it should but the colours were muted, almost sepia in tone and there was a ringing in my ears like the sensation you get when swimming near the bottom of the deep end. Molly was nowhere to be seen, but I thought I caught a glimpse of Nightingale, or at least the imprint of Nightingale on the stone memory, making his way wearily up the stairs. I unclasped my hand and checked that I was still ‘holding’ the skeleton badge. It was still there, and when I closed my fingers back around it I felt it tug, very gently, towards the south. I turned and made my way towards the side door in Bedford Place, but as I crossed the atrium floor I was suddenly aware of a vast darkness beneath my feet. It was as if the solid black and white tiles had been rendered transparent, and through them I could glimpse a terrible abyss – dark, bottomless and cold. I tried to move faster but it was like walking into a violent headwind. I had to lean forward and push hard to make progress. It wasn’t until I’d carefully steered myself through the narrow servants’ quarters under the east stairs that I wondered whether, this being the realm of ghosts, after all, I might just walk through the walls. After knocking my forehead a couple of times I just opened the side door like a normal person.

I stepped out into the 1930s and the stink of horses. I knew it was the 1930s because of the double-breasted suits and gangster hats. The cars were nothing but shadows, but the horses were solid and smelled of sweat and manure. There were people walking on the pavements; they looked perfectly normal but for an abstracted look in their eyes. I stepped in front of one man as an experiment, but he just walked around me as if I were a familiar and inconsequential obstacle. A sharp pain in my neck reminded me that I wasn’t here to sightsee.

I let the skeleton badge tug me onwards down Bed-ford Place and towards Bloomsbury Square. Above, the sky seemed strangely ill defined, blue at one moment, cloudy the next and then gritty with coal smoke. As I travelled I noticed that the clothes on the passers-by changed, the ghost cars vanished completely and even the skyline began to alter. I realised I was being drawn back in time through the historical record. If I had guessed right, then Nicholas Wallpenny’s badge would not only take me to his Covent Garden haunt but to the point in time when he started haunting it.