The Parish burial records were sketchy, and the best approximate position I could get for Wallpenny’s grave was over on the north side of the gardens, somewhere near the middle. Since Nicholas had been loath to show himself with Nightingale around, he was going to be stationed by the gate on Bedford Street, safely within screaming-for-help range. There was still the occasional trill of birdsong as I entered just after midnight. The night was clear, but you couldn’t see any stars through the haze. The iron of the gate was cold under my hand as I swung it closed and headed for the grave. I had a Canadian survival torch which came with a headband; I used it to read the crib notes in my standard-issue police notebook.

You cannot scratch a pentagram into soft, springy turf with anything less than a back hoe, and in any case I wasn’t about to vandalise such a lovely lawn. Instead I drew the star and circle with charcoal dust using a burlap sack with a hole cut in one corner like an icing bag. I laid it on nice and thick. Polidori had quite a lot to say about the dangers of breaking the pentagram when summoning a spirit. Having your soul dragged out and sent screaming down to hell was only the start of it.

At each cardinal point of the pentagram I put one of my calculators. I’d suggested that I bring Toby along just in case the substitution didn’t work, but when it was time to leave the Folly the dog was nowhere to be found. I’d picked up a packet of chemical glow sticks from a local camping shop, and these I cracked and placed where the crib sheet called for candles. The conjurer – in this case, me – was supposed to impart some of his essence, which was late eighteenth-century magic speak for ‘put some magic into’ the circle around the pentagram. There’s a particular forma created for just that purpose but I hadn’t had time to learn it – instead, Nightingale suggested that I just create a were-light in the centre.

I took a deep breath, created the werelight and floated it into the centre of the pentagram. I adjusted my light and started to read the conjuration from my notebook. The original had gone on for four manuscript pages, but with Nightingale’s help I’d managed to shave it down some.

‘Nicholas Wallpenny,’ I said. ‘Hear my voice, accept my gifts, rise and converse.’

And suddenly he was there, as shifty-looking as ever.

‘I knew you was special as soon as I laid eyes on you,’ he said. ‘Your governor not around, is he?’

‘Over there,’ I said, ‘beyond the gate.’

‘Mind you keep him there,’ said Nicholas. ‘I was right about the murdering gent, weren’t I?’

‘We think it’s the spirit of Pulcinella,’ I said.