It’s not easy manoeuvring an articulated lorry up the Wapping Wall, so I hired a middle-aged man called Brian to do it. Brian was balding, pot-bellied and foulmouthed. The only thing missing from the stereotype was a Yorkie Bar and a rolled-up copy of the Sun. Still, I hadn’t hired him for his erudition, and he did get us all the way to Mama Thames’s house without any extraneous insurance claims.

We parked up half outside Mama Thames’s block and half outside the Prospect of Whitby. The staff must have thought it was an unexpected delivery because they came tumbling out – I had to tell them it was for a private party, and weirdly they didn’t seem that surprised. I asked Brian to wait, and picking up my crate of samples from the cab, I staggered over to the communal entrance. I put it down and rang the doorbell. This time I was met at the door by the same white lady I’d seen before among Mama Thames’s cronies. She was dressed in a different, but equally nice, twinset and pearls, and carried a small black child on her hip.

‘Why Constable Grant,’ she said. ‘How lovely to see you again.’

‘Let me guess,’ I said. ‘You must be Lea.’

‘Very good,’ said Lea. ‘I do like a young man who has his wits about him.’ The River Lea rises in the Chilterns north-west of London, and skirts the top of the city before making a sharp right-hand turn down the Lea Valley to the Thames. It’s the least urbanised of London’s rivers and the largest, so of course it survived the great stink. Lea must have been one of Oxley’s generation of genii locorum, if not older.

I pulled a face at the child, who looked to be a girl of nursery age, and she pulled a face back. ‘Who’s this?’ I asked.

‘This is Brent,’ said Lea. ‘She’s the youngest.’

‘Hello Brent,’ I said. She was lighter-skinned than her sisters, with brown eyes that might have been called hazel by a good-natured liar, but the belligerent set of her face was unmistakable. She was wearing a miniature red England away strip, predictably the number 11 shirt.

‘You smell funny,’ said Brent.

‘That’s because he’s a wizard,’ Lea told her.

Brent squirmed out of Lea’s grip and grabbed my hand. ‘Come with me,’ she said and tried to drag me through the door. She was surprisingly strong, and I had to brace a little to stay still. ‘I have to bring my crate,’ I told her.

‘Don’t worry, I’ll take care of that,’ said Lea.

I let Brent pull me down the long cool corridor to Mama Thames’s flat. Behind me I heard Lea calling for Uncle Bailiff, and if he would be a dear, could he take the crate to Mama’s flat.

According to Dr Polidari, genii locorum ‘behave as if the imperatives of ceremony are to them as necessary as meat and drink is to man’, and furthermore claimed that they ‘anticipate such events with miraculous facility so that they are always appropriately attired, and if surprised or somehow prevented, show signs of great distress’. Given that he was writing in the late eighteenth century, I like to cut him some slack.

They were waiting for me in the throne room, and this time I could see it was a throne room, the potted mangrove sheltering the sacred World of Leather executive armchair. There sat Mama Thames, resplendent in her Austrian lace and a headdress of blue and white Portuguese beads. Behind her were arrayed her attendants in batik lappas and headscarves and on her left and right hands, forming an aisle down which I had to walk, stood her daughters. I recognised Tyburn and Fleet on my left standing with a pair of teenage girls wearing thin braids and cashmere jumpers. Beverley was on my right, looking underdressed in Lycra shorts and a purple sweatshirt. When she was sure I was looking she rolled her eyes. Beside her stood an amazingly tall and slender woman with a fox face, electric-blue and blonde extensions and elongated nails painted in green, gold and black. That, I guessed, was Effra, another underground river, who was clearly moonlighting as the goddess of Brixton market. I noticed that it was north London rivers on the left and south London rivers on the right.

Brent let go of my hand, essayed a curtsey in the direction of Mama Thames and then spoiled the effect by skipping over and hurling herself into her mother’s lap. There was a brief pause in the ceremony as the little girl squirmed her way into a comfortable position.

Mama Thames turned her full gaze on me, and the undertow of her regard drew me closer to her throne. I had to fight a strong urge to throw myself on my knees and bang my forehead on the carpet.

‘Constable Peter,’ said Mama Thames. ‘How nice to see you.’

‘It’s nice to be here. As a token of my respect I’ve brought you a gift,’ I said, hoping that it was going to arrive before I ran out of pleasantries. I heard clinking behind me, and Uncle Bailiff arrived with my crate. He was a heavyset white man with a number two skinhead and a faded tattoo of SS lightning bolts on his neck. He set the crate down before Mama Thames, gave her a respectful nod and, with a pitying look at me, left without a word.

One of the cronies stepped forward to pluck a bottle from the crate and show it to Mama Thames. ‘Star Beer,’ she said. The core product of the Nigerian Breweries PLC, available in the UK from any good stockist, and in bulk if your mum knows someone who knows someone who owes someone a favour.

‘How much has he got out there?’ asked Fleet.

‘A lorryload,’ said Lea.

‘How big a lorry?’ asked Mama Thames without taking her eyes off me.

‘Big lorry,’ said Brent.

‘Is it all Star?’ asked Mama Thames.

‘I put in some Gulder,’ I said. ‘Some Red Stripe for variety, a couple of cases of Bacardi, some Appleton, Cointreau and a few bottles of Bailey’s.’ I’d liquidated my savings doing it, but as my mum says, nothing worth having is free.

‘That’s a handsome gift,’ said Mama Thames.

‘You can’t be serious?’ said Tyburn.

‘Don’t worry, Ty,’ I said. ‘I threw in a couple of bottles of Perrier for you.’

Someone sniggered – probably Beverley.

‘And what can I do for you?’ asked Mama Thames.

‘It’s a small matter,’ I said. ‘One of your daughters feels that she has a right to interfere in the business of the Folly. All I ask is that she steps back and lets the proper authorities get on with their jobs.’

‘Proper authorities,’ spat Tyburn.

Mama Thames turned her eyes on Tyburn, who stepped before the throne. ‘You think you have a right to meddle in this?’ she asked.

‘Mum,’ said Tyburn. ‘The Folly is a relic, a Victorian afterthought from the same people who gave us Black Rod and the Lord Mayor’s show. Heritage is all very well and good for the tourist industry, but it’s no way to run a modern city.’

‘That is not your decision to make,’ I said.

‘And you think it’s yours?’

‘I know it’s mine,’ I said. ‘My duty, my obligation – my decision.’

‘And you’re asking—’

‘I am not asking,’ I said, pleasantries over. ‘You want to fuck with me, Tyburn, you had better know who you’re messing with.’

Tyburn took a step back and recovered. ‘We know who you are,’ she said. ‘Your father is a failed musician and your mother cleans offices for a living. You grew up in a council flat, and you went to your local comprehensive and you failed your A levels …’

‘I am a sworn constable,’ I said, ‘and that makes me an officer of the law. I am also an apprentice, which makes me a keeper of the sacred flame, but most of all I am a free man of London and that makes me a Prince of the City.’ I jabbed a finger at Tyburn. ‘No double first from Oxford trumps that.’

‘You think so?’ she said.

‘Enough,’ said Mama Thames. ‘Let him into his house.’

‘It’s not his house,’ said Tyburn.

‘Do as I say,’ said Mama Thames.

‘But Mum …’

‘Tyburn!’

Tyburn looked stricken, and for a moment I felt genuinely sorry for her because none of us is ever grown-up enough that our mothers don’t think they can’t beat us. She slipped a slimline Nokia from her pocket and dialled a number without taking her eyes off mine. ‘Sylvia,’ she said. ‘Is the Commissioner available? Good. Could I have a quick word?’ Then, having made her point to her own satisfaction, she turned and walked from the room. I resisted the urge to gloat but I did glance over at Beverley to see if she was impressed with me. She gave me a studiously indifferent look that was as good as a blown kiss.

‘Peter,’ said Mama Thames, and beckoned me over to her chair. She indicated that she wanted to tell me something private. I tried to bend down with as much dignity as I could but I found myself, much to Brent’s amusement, on my knees before her. She leaned forward and brushed her lips against my forehead.

For a moment it was as if I stood high up on the middle cowling of the Thames Barrier looking east over the mouth of the river. I could feel the towers of Canary Wharf rising triumphantly at my back and beyond them the docks, the White Tower and all the bridges, bells and houses of London town. But ahead of me over the horizon I could feel the storm surge, the fatal combination of high tides, global warming and poor planning, waiting. Ready to drive a wall of water ten metres high up the river and bring down the bridges, towers and Uncle Tom Cobley and all.

‘Just so you understand,’ said Mama Thames, ‘where the real power lies.’

‘Yes, Mama,’ I said.

‘I expect you to sort out my dispute with the Old Man,’ she said.

‘I’ll do my best,’ I said.

‘Good boy,’ she said. ‘And because of your good manners, I have a last gift.’ She bent her head and whispered a name in my ear: ‘Tiberius Claudius Verica.’

The paratroopers were gone by the time I got back to Russell Square. I was back in charge of the Folly, and also responsible. Toby slammed into my ankles as soon as I was across the threshold, panting and thrashing affectionately, although once he’d established that I wasn’t carrying anything edible he lost interest and scampered off. Molly was waiting for me at the foot of the western stairs. I told her that Nightingale was conscious and then lied and said that he’d asked how she was. I told her what I was planning to do and she physically recoiled.

‘I’m just going to my room to get some stuff,’ I said. ‘I’ll be back down in half an hour.’

As soon as I reached my room I pulled out my Latin notes and checked the stuff about Roman names. Which, I’d learned, often have three bits – praenomen, nomen and cognomen – and, if you can read your own handwriting, tell you a lot about the individual. Verica wasn’t a Latin name; I suspected it was British, and Tiberius Claudius were the first two names of Tiberius Claudius Caesar Augustus Germanicus, otherwise known as Emperor Claudius, him who was in charge when Britain was first conquered by the Romans. The Empire liked to co-opt the local ruling elite wherever possible – it being easier to get your leg over a country if you forked out for dinner and a dozen roses first. One of the bribes on offer was Roman citizenship, and many who took up that offer kept their native name and prefixed the praenomen and nomen of their sponsors – in this case the Emperor. Thus, just from the evidence of his name, Tiberius Claudius Verica was an aristocratic Briton who lived around the time the city was founded.

Which meant nothing, as far as I could tell. If I survived the next hour or so, I planned to have a word with Mama Thames about it. But I had more immediate problems.

*

In 1861 William Booth resigned from the Methodists in Liverpool and headed for London where, in the grand tradition of metropolitan reinvention, he founded his own church and took Christ, bread and social work to the heathen natives of east London. In 1878 he declared that he was tired of being called a volunteer and that he was a regular in the army of Christ or nothing at all; thus the Salvation Army was born. But no army, however pure its motives, occupies a foreign country without resistance, and this was provided by the Skeleton Army. Driven by gin, bone-headedness and growling resentment that being the Victorian working class was bad enough without being preached at by a bunch of self-righteous northerners, the Skeleton Army broke up Salvation Army meetings, disrupted marches and attacked its officer corps. The emblem of the Skeleton Army was a white skeleton against a black background – a badge worn by right-thinking ne’er-do-wells from Worthing to Bethnal Green. I’d spotted one on the ghostly form of Nicholas Wallpenny, a candidate for the Skeleton Army if ever there was one, and it was this badge that I’d recovered from the graveyard of the Actor’s Church. Nightingale had said that I was going to need a spirit guide, and in the absence of mystical bears, coyotes or whatever, a larcenous cockney was going to have to do.

The badge was where I’d left it, in the plastic box where I kept my paperclips. I picked it up and held it in the palm of my hand. It was just a cheap little thing, pewter and brass. When I closed my hand around it there was the fleeting taste of gin, old songs and just a little stab of resentment.

If this was to be a spiritual journey I wasn’t going to need anything else, and I’d put off the moment long enough. I went reluctantly downstairs to where Molly was waiting for me in the middle of the atrium. She stood with her head bowed, her hair a black curtain hiding her face, hands locked in front of her.

‘I don’t want to do this either,’ I said.

She raised her head, and for the first time looked me directly in the eye. ‘Do it,’ I said.

She moved so fast I didn’t see it, throwing herself against me. One arm snaked around my shoulders and grabbed the back of my head, the other went around my waist. I could feel her breasts pressing against my chest, her thighs clamping hard around my leg. Her face was buried in the hollow of my neck, and I felt her lips against my throat. Fear rolled over me: I tried to pull myself free but she held me tighter than a lover. I felt her teeth scrape at my neck and then pain, strangely more like a blow rather than a stab, as she bit me hard. I felt the action of her swallowing as she sucked at my blood but I also felt the connection with the tiles beneath me and the bricks in the walls – the yellow London clay – and then I was falling backwards into daylight and the smell of turpentine.

It wasn’t like a VR or a how you imagine a hologram should work; it was like breathing vestigia, like swimming in stone. I found myself in the Folly’s own memory of the atrium.

I’d done it – I was in.

*

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.

The most recent book on the subject I could find had been from 1936, and written by a guy called Lucius Brock. He’d speculated that vestigia were laid down in layers like archaeological deposits, and that different spirits inhabited different layers. I was going to Wall-penny in the late Victorian era and he was going to lead me to Henry Pyke in the late eighteenth century and Pyke, whether he wanted to or not, would reveal his last resting place.

I’d made it as far as the top of Drury Lane when the Victorian era drove me retching to my knees. I’d been getting used to the pervading smell of horseshit but the 1870s was like sticking your head into a cesspit. It may have been vestigia, but it was strong enough to heave my imaginary lunch into the filthy gutter. I tasted blood in my mouth and realised that some of that was my own – no doubt fuelling whatever occult shit Molly was doing to keep me here.

Bow Street was crammed with enormous carts and high-sided vans drawn by horses the size of decent family hatchbacks. This was Covent Garden at its height, and I expected Wallpenny’s skeleton badge to lead me down Russell Street to the Piazza but instead it pulled me to the right, up Bow Street, towards the Royal Opera House. Then the carts changed shape and I realised that I was too far back in time and that something had gone wrong with Plan A.

As if being cleared for the start of the next scene, the heavy carts vanished from outside the Opera House. The sky dimmed and the street became dark, lit only by torches and oil lamps. The ghost images of gilded carriages drifted past me while bewigged and perfumed ladies and gentlemen promenaded up and down the steps of the old Theatre Royal. A group of three men caught my eye. They seemed to be more solid than the other figures, denser and more real. One of them was a large elderly man in a big wig who walked stiffly with the aid of a stick – this had to be Charles Macklin. The light clung to him as if he were being singled out for a close-up – no prizes for guessing who by.

This, I assumed, was going to be a re-enactment of the infamous murder of Henry Pyke by the dastardly Charles Macklin and, right on cue, enter Henry Pyke in velvet coat and a state of high emotion, his wig askew and an outsized stick in his hand.

Only, I recognised the face. I’d first seen it on a cold January morning and it had introduced itself as Nicholas Wallpenny – late of the Parish of Covent Garden. But no, not Nicholas Wallpenny, it was Henry Pyke. It was always Henry Pyke, right from the start, from the portico of the Actor’s Church, making the most of his chirpy cockney impression. Well, at least it explained why Wallpenny wouldn’t show himself in front of Nightingale. It also meant that the scene at the church that had led me to my impromptu excavation of a priceless London landmark had been just that – a scene, a performance.

‘Help, help,’ cried one of Macklin’s companions, ‘murder!’

Some things are universal: birds got to fly, fish got to swim, fools and policemen got to rush in. I managed to restrain myself from shouting ‘oi’ as I ran forward, and as a result got within two metres before Henry Pyke saw me coming. I got a very satisfying ‘oh fuck’ expression from him and then his face changed – he became the ludicrous quarter-moon caricature that I had come to know as Mr Punch, spirit of riot and rebellion.

‘You know,’ he squeaked, ‘you’re not nearly as stupid as you look.’

Standard operating procedure for dealing with mad fuckers; keep them talking, sidle closer, grab them when they ain’t looking.

‘So was that you pretending to be Nicholas Wall-penny?’

‘No,’ said Mr Punch. ‘I let Henry Pyke do all the deception, lives to act, poor thing, it’s all he ever wanted out of life.’

‘Except he’s dead,’ I said.

‘I know,’ said Mr Punch. ‘Isn’t the universe wonderful?’

‘Where’s Henry now?’

‘He’s in your girlfriend’s head having carnal knowledge of her brain,’ said Mr Punch, and then threw back his head and shrieked with laughter. I lunged but the slippery bastard turned on his heel and legged it down one of the narrow alleys that connected to Drury Lane.

I took off after him, and I’m not saying that I could feel the spirit of every London thief taker flowing through me as I ran, but consider – we did start outside Bow Street Magistrates Court, and I could no more have not chased him than I could have stopped breathing.

I burst out of the alley onto a winter’s Drury Lane, pedestrians bundled into anonymity, steam rising from the horses and the men who carried the sedan-chairs. In the rush of cold and snow the city smelled clean and fresh and about to be rid of one irritating revenant spirit. Spring came with a stuttering stop-start motion swiftness, and Mr Punch led me down grimy side streets that I knew didn’t exist any more until finally we passed a newly built St Clements and onto Fleet Street. The great fire of London went by too fast for me to register it, just a blast of hot air as if from the open door of an oven. One minute the top of Fleet Street was dominated by St Paul’s, and the next the dome had been replaced by the squared-off Norman tower of the old cathedral. To a Londoner like me it was a heretical sight – like suddenly finding a stranger in your bed. The street itself was narrower and crowded by narrow-fronted half-timbered houses with overhanging upper floors. We were back in the time of Shakespeare, and I have to say it didn’t smell nearly as bad as the nineteenth century. Mr Punch was running for his afterlife, but I was gaining.

London was also shrinking. Gaps were opening in the buildings on either side. I could see green pastures with hayricks and herds of cows. Things were losing focus around me. Ahead the River Fleet appeared, and suddenly I was dipping down to cross a stone bridge, while on the other side of the valley there were walls – the ancient walls of London. I only just made it through Ludgate before the actual gates had grown back and barred my way. The old cathedral was long gone; we’d missed the Anglo-Saxons and what modern go-ahead historians like to call the sub-Roman period, and paganism was back in fashion.

If I’d been thinking about it, I probably should have stopped and had a good look around, answered a few important questions about life in Londinium, but I didn’t because that’s when I closed the last couple of metres on Mr Punch and rugby-tackled the dead fucker to the ground.

‘Mr Punch,’ I said. ‘You’re nicked.’

‘Bastard,’ he said. ‘Black Irish bastard dog.’

‘You’re not making yourself any friends here, Punch,’ I said. I got him back on his feet with both his arms jacked far enough up behind his back that he wasn’t going anywhere without at least a broken elbow.

He stopped squirming and turned his head until he could watch me with one eye. ‘So you got me, copper,’ he said. ‘What are you going to do with me now?’

It was a good question, and a sudden savage pain in the hollow of my throat reminded me that I was running out of time.

‘Let’s see what the hanging magistrate makes of you,’ I said.

‘De Veil?’ asked Mr Punch. ‘Yes please, I’m sure he’ll be delicious.’

Revenant, spirit of riot and rebellion, I thought, you idiot. He eats ghosts. I needed something stronger. Brock had written that the genii locorum, the gods and spirits of place, were stronger than ghosts. Was there a god of justice? And where would I find him – or maybe her? Then I remembered: a statue of a woman stands atop the dome of the Old Bailey. In one hand she holds a sword and a set of scales. I didn’t know if there was a goddess of justice or not, but I was willing to bet big money that Mr Punch would know.

‘Why don’t we go and ask the nice lady of the Old Bailey?’ I suggested.

He tensed, and I knew I’d bet right. He struggled again and slammed his head back, aiming for my chin, but that isn’t exactly a new one for a policeman, so I had my head back safely out of reach.

‘You’re going up the steps this time,’ I said.

Mr Punch went limp, defeated I thought, but then he began to shake in my grip. At first I thought he was crying, and then I realised it was laughter. ‘You’re going to find that a bit difficult,’ he said. ‘You seem to have run out of city.’

I looked around and saw that he was right. We’d gone back too far, and now there was nothing left of London but huts and the wooden stake rampart of the Roman camp to the north. There was no stonework at all, nothing but the new-cut smell of oak planking and hot pitch. Only one thing stood complete – the bridge. It was less than a hundred metres away and constructed of square-cut timbers. It looked more like a fishing pier that had got ideas above its station and crossed the river in a fit of exuberance.

I could see a crowd halfway across, sunlight flashing off the brass fittings of a file of legionnaires standing at attention. Beyond them a cluster of civilians in togas chalked to a blinding white for a special occasion and watching a couple of dozen men, women and children in barbaric trousers and brass torcs.

Suddenly I understood what it was Mama Thames had been trying to tell me.

I think Mr Punch understood as well, because he fought me all the way as I dragged him across the bridge and in front of the toga-clad officials. These were more echoes from the past, memories trapped in the fabric of the city – they didn’t react when I threw Punch down before them. I was in Year Five when we did Roman history at school, so we didn’t learn a lot of dates but we did do plenty of group work on what it was like to live in Roman Britain. Which was why I could recognise the officiating priest by the purple-striped stole that covered his head. I could also recognise him by his face, although he looked a lot younger than he had when I’d seen him in the flesh. Plus he was clean-shaven and his black hair hung around his shoulders, but it was the same face that I had last seen propping up a fence at the source of the Thames. It was the spirit of the Old Man of the River as a young man.

Suddenly a great many things became clear to me.

‘Tiberius Claudius Verica,’ I called.

Like a man emerging from a daydream, the priest turned his eyes to me. When he saw me he broke into a delighted grin. ‘You must be my gift from the gods,’ he said.

‘Help me, Father Thames,’ I said.

Verica plucked a pilum from the hands of the nearest legionary – the soldier didn’t react – and handed it to me. I smelled freshly cut beech wood and wet iron. I knew what to do. I upended the heavy spear and hesitated. Mr Punch shrieked and bellowed in his strange, reedy high-pitched voice. ‘Isn’t it a pity about pretty pretty Lesley,’ he squealed. ‘Will you still love your pretty little Lesley when her face has fallen off?’

This is not a person, I told myself, and drove the pilum into Mr Punch’s chest. There was no blood, but I felt the shock as it pierced skin, muscle and finally the wooden planking of the bridge itself. The revenant spirit of riot and rebellion was pinned like a butterfly in its display case.

And people say modern education is a waste of time.

‘I asked the river to give us a sacrifice,’ said Tiberius Claudius Verica, ‘and a sacrifice was provided.’

‘I thought the Romans frowned on human sacrifice,’ I said.

Verica laughed. ‘The Romans haven’t arrived yet,’ he said.

I looked around. He was right, there was no trace of London – or the bridge. For a moment I hung suspended like a cartoon character, and then I fell into the river. The Thames was cold and as fresh as any mountain stream.

I came up feeling horribly wet and sticky. There was blood smeared over my chest and I’d wet myself at some point, probably when she’d bitten me. I felt drained and voided and numb. I wanted to curl up and pretend that nothing was real.

‘That,’ I said, ‘is never going to catch on as a tool for historical research.’

Somebody was retching but amazingly it wasn’t me. Molly was hunched over, her face turned away and hidden by her hair, vomiting blood onto her nice clean tiles. My blood, I thought, and climbed to my feet. I was light-headed but I wasn’t falling over – that had to be a good sign. I took a step towards Molly to see if she was okay, but she flung her arm in my direction, palm out, and made violent pushing gestures, so I backed off.

I found myself sitting down again without any memory of wanting to. I was short of breath and I could feel my pulse racing in my throat – all symptoms of blood loss. I decided that it would be a good idea to have a little rest, and I lay back down on the cool tiles, all the better to maintain the blood flow to my brain. It’s surprising how comfortable a hard surface can be when you’re tired enough.

The rustle of silk made me turn my head. Molly, still crouching, had turned away from the slick pool of red vomit and inched towards me. Her head was tilted to one side and her lips were drawn back to reveal her teeth. I was just about to tell her that I was all right really, and didn’t need any help, when I realised that was probably not what she had in mind.

With a disturbingly spider-like motion Molly swung one arm over her head and down until her hand slapped on the tiles in front of her face. The arm tensed and dragged Molly another few centimetres towards me. I looked into her eyes and saw that they were all black, with no trace of white at all, and filled with hunger and despair.

‘Molly,’ I said, ‘I really don’t think this is a good idea.’

Her head tilted the other way and she made a gurgling, hissing sound, halfway between laughter and a sob. Sitting up gave me tunnel vision and dizziness, and I fought the urge to lie back down again.

‘You think you’re conflicted now,’ I said. ‘Just think how you’ll feel when Nightingale finds out you had me for dinner.’

Nightingale’s name made her pause, but only for a moment. Then her other hand swept over her head and slapped down right next to my leg. I snatched it away as best as I could and managed to gain a metre in separation.

This only seemed to aggravate her, and I watched as she drew her legs up under her torso. I remembered how fast she’d moved when she first bit me, and wondered if I’d even seen her coming. Still, I wasn’t about to sit still and let her take me without a fight. I started putting a fireball together, but the forma was suddenly slippery and impossible to imagine.

Molly snorted and her head twisted on its side as if her neck had become as flexible as a snake. I could see the tension building in the curve of her back and the hunch of her shoulders. I think she could sense me trying to do magic, and didn’t think she was going to give me a chance to succeed. Her mouth opened too wide and displayed too many pointed teeth, and the squeaky little mammal in my ancestry started my legs scrambling in a mad attempt to propel myself backwards.

A brown shape smelling of damp carpet streaked past me and came to a halt, claws skidding on the tiles, between Molly and me. It was Toby in full primeval circle-of-the-campfire, man’s-best-friend, oh-that’s-why-we-domesticated-the-sodding-things mode, barking at Molly so hard his front paws were bouncing off the floor.

To be honest, Molly probably could have leaned forward and bitten Toby’s snout off, but instead she flinched backwards. Then she leaned forward again and hissed. This time Toby flinched, but he kept his ground in the long tradition of small scrappy dogs that are too stupid to know when to back down. Molly reared back on her haunches, her face a mask of anger and then, as if a switch had been pulled, she slumped down on her knees. Her hair fell back down to cover her face and her shoulders shook – I think she might have been sobbing.

I dragged myself to my feet and staggered towards the back door. I was thinking that it was probably best to put temptation out of harm’s way. Toby came trotting after me with his tail wagging. I bounced off the doorjamb and found myself outside in the sunlight facing the wrought-iron staircase that led up to the coach house. I contemplated the stairs and thought that I should have fitted a lift, or at least got a bigger dog.

I knew something else was wrong when Toby wouldn’t come all the way up the stairs. ‘Stay, boy,’ I said, and he dutifully sat on the landing and let me do the heroics. I considered walking away, but I was just too knackered to care and besides, this was my space with my flat-screen TV and I wanted it back.

I stood to one side of the door and pushed it open with my foot before gingerly peering around the jamb to see who was there. It was Lesley, waiting for me on the chaise longue holding Nightingale’s cane across her knees and staring into space. She glanced over as I slipped in.

‘You killed me,’ she said.

‘Can’t you just go back to wherever it was you came from?’

‘Not without my friend,’ she said. ‘Not without Mr Punch. You’ve murdered me.’

I slumped down in the easy chair. ‘You’ve been dead for two hundred years, Henry,’ I said. ‘I’m fairly certain you can’t murder someone who’s already dead.’ If you could, I thought, the Met would have a form for it.

‘I beg to differ,’ said Lesley. ‘Though it must be said that I have proved a failure on both sides of the veil.’

‘I don’t know,’ I said. ‘You had me fooled.’

Lesley turned and looked at me. ‘I did, didn’t I,’ she said.

I could see the thin pale lines of stretch marks around the bridge of Lesley’s nose, the fine tracery of broken blood vessels that started around her mouth and climbed like a winter vine to her cheeks. Even the way she spoke was different, the words slurred by broken teeth and Henry Pyke’s need to keep the mouth closed to hide the damage. I had to suppress the anger that seemed to boil up through my chest because this was a hostage situation, and the first rule of the hostage negotiator is never get emotionally involved. Or perhaps it was ‘don’t kill the kidnapper until the hostages are released’ – it was bound to be one or the other.

‘Looking back,’ I said, ‘it seems the more remarkable to me that you never slipped up once.’

‘You never suspected?’ asked Lesley, happily.

‘No,’ I said. ‘You were utterly convincing.’

‘A female role is always a challenge,’ said Lesley. ‘And a modern woman doubly so.’

‘It’s too bad she has to die,’ I said.

‘I want you to know that nobody was more surprised than I to find myself occupying this vessel,’ said Lesley. ‘I blame it on the Italian, Piccini, a passionate race. They have to incorporate lust into all their endeavours – even their religious works.’

I nodded and looked interested. Despite being plugged in, the TV and DVD standby lights were dark. Lesley had been sitting there long enough to drain all my electronics, and if they were gone then surely Lesley’s brain was going to be next. I had to get the last remains of Henry Pyke out of her head.

‘That’s how it is with a play,’ said Lesley. ‘The scenes and acts being so much more ordered than in the humdrum world. Unless one takes care, one can be swept away by the genius of the character. Thus Pulcinella made fools of us both.’

‘But you’d rather Lesley lived?’ I asked.

‘Is this possible?’ she asked.

‘Only if you agree,’ I said.

Lesley leaned forward and took my hand. ‘Oh, but I do, my boy,’ she said. ‘We can’t have it be said that Henry Pyke was so ungracious as to inflict his own sad fate upon an innocent.’

I really did wonder when he said that if he had any inkling of the trail of death and misery he’d left behind. Perhaps that was a function of being a ghost; perhaps to the dead the world of the living was a dream, and not to be taken too seriously.

‘Then let me call my doctor,’ I said.

‘This would be the Scottish Mohamedan?’

‘Dr Walid,’ I said.

‘You believe he can save her?’ asked Lesley.

‘I believe he can,’ I said.

‘Then by all means summon him,’ said Lesley.

I went outside onto the staircase, replaced the battery in my spare mobile and called Dr Walid, who said he would arrive within ten minutes. He gave me some instructions to follow in the meantime. Lesley looked expectant when I returned.

‘Can I have Nightingale’s staff?’ I asked.

Lesley nodded and handed over the silver-topped cane. I placed my hand on the handle as Dr Walid had suggested but there was nothing, just the chill of metal – the staff had been completely drained of magic.

‘We don’t have much time,’ I said. There was a relatively clean dust sheet over the back of the chaise longue – I grabbed it.

‘Truly?’ asked Lesley. ‘Alas, for as the hour grows closer I feel myself reluctant to depart.’

I started ripping the sheet into broad strips. ‘Can I speak to Lesley directly?’ I asked.

‘Of course, dear boy,’ said Lesley.

‘Are you okay?’ There was no outward change that I could see.

‘Ha,’ she said, and I was sure from the tone that this was the real Lesley. ‘That’s a stupid question. It’s happened, hasn’t it, I can feel it …’

She raised her hand to her face, but I took it and gently guided it back down.

‘Everything’s going to be OK,’ I said.

‘You’re such a bad liar,’ she said. ‘No wonder I had to do all the talking.’

‘You had such a natural talent for it,’ I said.

‘It wasn’t talent,’ said Lesley. ‘It was hard work.’

‘You always had such a natural talent for hard work,’ I said.

‘Bastard,’ she said. ‘I don’t remember them telling me when I joined that there was a risk my face might fall off.’

‘Don’t you?’ I asked. ‘Remember Inspector Neblett, old shovel-face himself? Maybe that’s what happened to him.’

‘Tell me I’m going to be okay again.’

‘You’re going to be okay,’ I said. ‘I’m going to hold your face on with this.’ I showed her the strips of sheet.

‘Oh well, that fills me with confidence,’ she said. ‘Promise you’ll be there whatever happens?’

‘I promise,’ I said and, following Walid’s instructions, started winding a strip of the sheet tightly around her head. She mumbled something, and I assured her that I’d cut a hole for her mouth when I’d finished. I secured the sheet the way one of my mum’s sisters had taught me to secure a headscarf.

‘Oh good,’ said Lesley once I’d cut the promised hole. ‘Now I’m the invisible woman.’ Just to be on the safe side, I knotted the material at the back of her neck to maintain the tension. I found a bottle of Evian by the chaise longue and used it to soak the makeshift bandage.

‘You’re trying to drown me now?’ asked Lesley.

‘Dr Walid told me to do this,’ I said. I didn’t tell her that it was to stop the bandage sticking to the wounds.

‘It’s cold,’ she said.

‘I’m sorry,’ I said. ‘I’m going to need Henry back.’

Henry Pyke returned with transparent eagerness. ‘What must I do now?’

I cleared my mind and opened my hand and spoke the word – ‘Lux!’ A werelight flowered above my hand. ‘This is the light that will take you to your place in history,’ I said. ‘Take my hand.’ He was reluctant. ‘Don’t worry, it won’t burn you.’

Lesley’s hand closed around mine, light leaking out between her fingers. I didn’t know how long my magic would last, or even if the whole blood-sucking business with Molly had left me much magic in the first place. Sometimes you just have to hope for the best.

‘Listen, Henry,’ I said. ‘This is your moment, your big exit. The lights will dim, your voice will fade, but the last thing the audience will see is Lesley’s face. Hold on to the image of her face.’

‘I don’t want to go,’ said Henry Pyke.

‘You must,’ I said. ‘That’s the mark of true greatness in an actor – knowing, down to the precise moment, when to make his exit.’

‘How wise of you, Peter,’ said Henry Pyke. ‘That is the true mark of genius, to give oneself to one’s public but to retain that private side, that secret space, that unknowable …’

‘To leave them wanting more,’ I said, trying to keep the desperation out of my voice.

‘Yes,’ said Henry Pyke, ‘to leave them wanting more.’

And then the mouthy git was gone, right on cue.

I heard heavy footsteps on the iron staircase. Dr Walid and the cavalry had arrived. Red stains immediately bloomed on the white sheets covering Lesley face. I heard her gurgling and choking as she tried to breathe. A big hand landed on my shoulder and unceremoniously pushed me out of the way.

I let myself fall to the floor – I figured I could catch up on some sleep now.