He was a middle-aged white man in a good-quality but otherwise nondescript bespoke suit. He held what looked like a semi-automatic pistol in his right hand and a Kobbé’s opera guide in his left. He wore a white carnation in his buttonhole.

Nightingale fell down quickly. He just slipped to his knees and flopped forward onto his face. He let go of his cane and it rattled on the paving stones.

The man in the good suit looked at me, his eyes pale and colourless in the sodium light of the streetlamps, and winked. ‘That’s the way to do it,’ he said.

You can run away from a man with a handgun, especially in poor lighting conditions, provided you remember to zigzag and can open the range fast enough. I’m not saying that option wasn’t tempting, but if I ran then there was nothing to stop the gunman from stepping forward and shooting Nightingale in the head. I was trained to placate the gunman while edging backwards; talking establishes a rapport and keeps the suspect’s focus on the officer so that the civilians can get clear. Ever see The Blue Lamp with Jack Warner and Dirk Bogarde? During our training at Hendon, they made us watch the scene where PC Dixon, Warner’s character, is shot dead. The film was written by an ex-copper who knew what he was talking about. Dixon dies because he’s a dinosaur who stupidly advances on an armed suspect. Our instructors were clear: don’t crowd, don’t threaten, keep talking and backing away, a suspect has to be particularly stupid, political or, in one memorable case, protected by diplomatic immunity to think that killing a police officer will in any way make their situation any better. At the very least you’re buying enough time for an armed response team to arrive and blow the silly bugger’s head off.

I didn’t think that backing off was an option. This was one of Henry Pyke’s sequestrated puppets, and wouldn’t hesitate to shoot me or Nightingale no matter how calmly I was talking.

To be honest, I didn’t think at all. My brain went: Nightingale down – gun – spell!

‘Impello!’ I said as calmly as I could, and levitated the man’s left foot one metre in the air. He screamed as his body was catapulted upwards and to the right. I must have lost concentration because I heard the distinct crack of a bone breaking in his ankle. The gun fell out of his hand and his arms flailed as he tumbled to the ground. I stepped forward and kicked the gun down the street, then kicked him once in the head, hard, just to make sure.

I should have cuffed him, but Nightingale was lying in the road behind me making wet breathing sounds. It was what they call a ‘sucking chest wound’, and they’re not being metaphorical in their description. There was an entry wound ten centimetres below Nightingale’s right shoulder, but at least when I gently rolled him on his side I couldn’t find an exit wound. My first-aid training was unequivocal about sucking chest wounds – every second you spend faffing around is another second that the London Ambulance Service hasn’t arrived.

I knew that the back-up teams couldn’t have heard the gunshot because they’d have been there already, and I’d blown my Airwave when I levitated the gunman off his feet. Then I remembered the silver whistle in the top pocket of my uniform jacket. I fumbled it out, put it in my mouth and blew as hard as I could.

A police whistle on Bow Street. For a moment I felt a connection, like a vestigium, with the night, the streets, the whistle and the smell of blood and my own fear, with all the other uniforms of London down the ages who wondered what the hell they were doing out so late. Or it could just have been me panicking; it’s an easy mistake to make.

Nightingale’s breath started to falter.

‘Keep breathing,’ I said. ‘It’s a habit you don’t want to break.’

I heard sirens coming closer – it was a beautiful sound.

The trouble with the old boy network is you can never really be sure whether it’s switched on or not, and whether it’s operating in your interest or some other old boy’s. I began to suspect that it wasn’t operating in my interest when they brought a cup of coffee and a biscuit to the interview room. Fellow police officers being interviewed in a friendly manner get to go to the canteen and fetch their own coffee. You only get room service when you’re a suspect. I was back in Charing Cross nick, so it wasn’t as if I didn’t know the way to the canteen.

Inspector Nightingale was still alive, they told me that much before they sat me down on the wrong side of the interview table, and had been taken to the brand new trauma centre at UCH listed as ‘stable’, a term which covered a multitude of sins.

I checked the time. It was three thirty in the morning, less than four hours after Nightingale had been shot. If you work for any time in a large institution you start to get an instinctive feel for its bureaucratic ebb and flow. I could feel the hammer coming down, and since I’d only been a copper for two years, the fact that I could feel it coming meant that it was a very big hammer indeed. I had a shrewd idea about who’d put the hammer in motion, but there was nothing I could do but stay sitting on the wrong side of the interview table with my cup of bad coffee and two chocolate biscuits.

Sometimes you have to stand still and take the first blow. That way you can see what the other man has in his hand, expose his intentions and, if that sort of thing is important to you, put yourself unequivocally on the right side of the law. And if the blow is so heavy that it puts you down? That’s just a risk you have to take.

The blunt instrument chosen caught me by surprise, although I made sure I kept my face neutral when Seawoll and Detective Sergeant Stephanopoulos entered the interview room and sat down opposite me. Stephanopoulos slapped a folder down on the table. It was far too thick to have been generated in the last couple of hours, so most of it must have been padding. She gave me a thin smile as she ripped the cellophane off the audio cassettes and slotted them into the dual tape machine. One of those tapes was for me, or my legal representative, to prevent me being quoted out of context; the other was for the police to prove that I had copped to the charge without them having to beat me around the back, thighs and buttocks with a sock full of ball bearings. Both of the tapes were redundant because where I sat was neatly framed in the viewfinder of a CCTV camera mounted just above the door. The live feed went to the observation room down the corridor where, judging from the theatrical way Seawoll and Stephanopoulos had made their entrance, someone of ACPO rank was watching – the Deputy Assistant Commissioner at the very least.

The tape machine was turned on, Seawoll identified me, himself and Stephanopouois as being present and reminded me that I was not under arrest but merely helping police with their inquiries. Theoretically I could stand up and walk out any time I liked, provided I didn’t mind kissing my career in the police goodbye. Don’t think I wasn’t tempted.

Seawoll asked me, for the record, to outline the nature of the operation that Nightingale and I had been running when he was shot.

‘You really want that on the record?’ I asked.

Seawoll nodded, so I gave the full account: our theory that Henry Pyke was a revenant, a vampire ghost bent on revenge who was acting out the traditional story of Punch and Judy using real people as puppets, and that together we had devised a way to put ourselves into the story so that Nightingale could track Henry Pyke’s bones and destroy them. Stephanopoulos couldn’t suppress a wince when I talked about the magical aspects of the case – Seawoll was unreadable. When we got to the shooting he asked me whether I recognised the gunman.

‘No,’ I said. ‘Who is he?’

‘His name is Christopher Pinkman,’ said Seawoll, ‘and he denies that he shot anyone. He claims he was walking home from the opera when two men attacked him in the street.’

‘How does he explain the gun?’ I asked.

‘He claims there wasn’t a gun,’ said Seawoll. ‘He stated that the last thing he remembers was leaving the opera, and the very next thing is being kicked in the head by you.’

‘That and the excruciating pain from the fractured bones in his lower leg,’ said Stephanopoulos. ‘Plus some serious bruising and contusions from when he was thrown to the ground.’

‘Was he tested for gunshot residue?’ I asked.

‘He teaches chemistry at Westminster School,’ said Stephanopoulos.

‘Bugger,’ I said. The gunshot residue test was notoriously unreliable, and if the suspect handled chemicals for a living then no forensic witness on earth was going to testify in court that it was likely, let alone conclusive, that he’d fired a gun. A horrible suspicion formed in my mind.

‘You did find a gun – right?’ I asked.

‘No firearm was recovered from the scene,’ said Stephanopoulos.

‘I kicked it along the pavement,’ I said.

‘No firearm was recovered,’ said Stephanopoulos slowly.

‘I saw it,’ I said. ‘It was a semi-automatic pistol of some sort.’

‘Nothing was found.’

‘Then how did Nightingale get shot?’ I asked.

‘That,’ said Seawoll, ‘is what we were hoping you could tell us.’

‘Are you suggesting I shot him?’

‘Did you?’ asked Stephanopoulos.

My mouth was suddenly dry. ‘No,’ I said. ‘I didn’t shoot him, and if there’s no gun, what am I supposed to have not shot him with?’

‘Apparently you can move things around with your mind,’ said Stephanopoulos.

‘Not with my mind,’ I said.

‘Then how?’ asked Stephanopoulos.

‘With magic,’ I said.

‘Okay, with magic,’ said Stephanopoulos.

‘How fast can you move something?’ said Seawoll.

‘Not as fast as a bullet,’ I said.

‘Really,’ said Stephanopoulos.

‘How fast is that?’

‘Three hundred and fifty metres per second,’ I said. ‘For a modern pistol. Higher for a rifle.’

‘What’s that in old money?’ asked Seawoll.

‘I don’t know,’ I said. ‘But if you lend me a calculator I can work it out.’

‘We want to believe you,’ said Stephanopoulos, playing the role of most unlikely ‘good cop’ in the history of policing. I made myself pause and take a deep breath. I hadn’t done any advanced interview courses but I knew the basics, and the conduct of this interview was far too sloppy. I looked at Seawoll and he gave me the ‘at last he wakes up’ look so beloved of teachers, senior detectives and upper-middle-class mothers.

‘What do you want to believe?’ I asked.

‘That magic is real,’ Seawoll said, and gave me a knowing smile. ‘Can you give us a demonstration?’

‘That’s not a good idea,’ I said. ‘There could be side effects.’

‘Sounds a bit too convenient to me,’ said Stephanopoulos. ‘What kind of side effects?’

‘Probably destroy your mobile phones, palm pilot, laptop or any other electronic equipment in the room,’ I said.

‘What about the tape recorder?’ asked Seawoll.

‘That too,’ I said.

‘And the CCTV?’

‘Same as the tape recorder,’ I said. ‘You can protect the phones by disconnecting them from their batteries.’

‘I don’t believe you,’ said Stephanopoulos, and leaned forward aggressively, neatly masking from the camera behind her the fact that she was popping the battery from her very ladylike Nokia slimline.

‘I think we’re going to want a demonstration,’ said Seawoll.

‘How much of a demonstration?’ I asked.

‘Show us what you’re made of, son,’ said Seawoll.

It had been a really long day and I was knackered, so I went for the one forma I can reliably do in a crisis – I made a werelight. It was pale and insubstantial under the fluorescent strip lighting and Seawoll wasn’t impressed, but Stephanopoulos’s heavy face broke into such a wide smile of unalloyed delight that for a moment I saw her as a young girl in a pink room full of stuffed unicorns. ‘It’s beautiful,’ she said.

One of the tapes unspooled messily inside the tape machine while the other just stopped dead. I knew from my experiments that I needed to up the strength of the werelight to take out the camera. I was going for a brighter light when the ‘shape’ in my mind went wrong and suddenly I had a column of light hitting the ceiling. It was a bright blue colour, and focused. When I moved my hand the beam played across the walls – it was like having my own personal searchlight.

‘I was hoping for something a bit more subtle,’ said Seawoll.

I shut the light down and tried to remember the ‘shape’, but it was like trying to remember a dream, slipping away even as I grabbed for it. I knew I was going to have to spend a long time in the lab trying to recapture that form, but as Nightingale had said right at the beginning, knowing the forma is there is half the battle.

‘Did that do for the camera?’ asked Seawoll. I nodded and he gave a sigh of relief. ‘We’ve got less than a fucking minute,’ he said. ‘I haven’t seen this much shit rolling downhill since de Menezes got shot, so my advice to you, son, is to find the deepest hole you can crawl into and stay there until this shitfall is over and the crap lies deep and crisp and even.’

‘What about Lesley?’ I asked.

‘I wouldn’t worry about Lesley,’ said Seawoll. ‘She’s my responsibility.’

Which meant that Seawoll had stepped in as Lesley’s patron and made it clear that anyone trying to get to her would have to go through him first. Since my patron was currently lying on a bed at UCH and breathing through a tube, Nightingale was unlikely to do the same for me. I like to think that Seawoll would have extended his protection to me if he could have, but I’ll never know for sure. He didn’t tell me that I should look out for myself – that was a given.

‘What the fuck do we do next?’ asked Seawoll.

‘You’re asking me?’

‘No, I’m fucking asking the table,’ said Seawoll.

‘I don’t know,’ I said. ‘Sir. There’s loads of stuff I don’t know.’

‘Then you’d better start educating yourself, Constable,’ said Seawoll. ‘Because I don’t know about you, but I don’t think Mr Henry Pyke is going to stop now – do you?’

I shook my head.

Stephanopoulos grunted and tapped her watch.

‘I’m going to spring you,’ he said. ‘Because we need to put an end to this fucking spiritual shit before some ACPO wallah panics and decides to bring in the Archbishop of Canterbury.’

‘I’ll do my best,’ I said.

Seawoll gave me a look that implied my best had better be fucking good enough. ‘When we start again,’ he said, ‘I need you to make sure your brain is engaged before you put your mouth into gear. Just like after the thing in Hampstead – clear?’

‘Crystal,’ I said.

The door to the interview room slammed open and a man stuck his head inside. He was middle-aged with greying hair, broad-shouldered and with extraordinarily bushy eyebrows. Even if I hadn’t recognised him from his web profile, I would have known Deputy Assistant Commissioner Richard Folsom was one of the big beasts of the jungle. He crooked his finger at Seawoll and said, ‘Alex, a word please.’

Seawoll looked at the ruined tape machine. ‘Interview suspended,’ he said and gave the time. Then he rose and meekly followed Folsom out of the room. Stephanopoulos gave me a half-hearted attempt at her famous evil glare, but I was wondering whether she still had her My Little Pony collection.

Seawoll returned and told us that we would be continuing the interview in an adjacent room, one where the monitoring equipment was still working. There, we continued the time-honoured tradition of brazenly lying through our teeth while telling nothing but the truth. I told them that Nightingale and I had reason to believe, through an entirely conventional informer, that the group – because it had to be more than one person – who had perpetrated a series of senseless attacks in and around the West End would be based on Bow Street, and that we had been investigating there when we were ambushed by unknown assailants.

‘Deputy Assistant Commissioner Folsom is particularly worried about any threat to the Royal Opera House,’ said Seawoll. Apparently he was a bit of a connoisseur, having been introduced to Verdi soon after rising to the rank of Commander. A sudden attack of culture snobbery is a common affliction among policemen of a certain rank and age; it’s like a normal midlife crisis only with more chandeliers and foreign languages.

‘We think that the focus of activity may be on Bow Street,’ I said. ‘But as yet our investigations have discovered no tangible link to the Royal Opera House.’

By six o’clock we ended up with a statement of events that Seawoll could sell to Folsom, and I was falling asleep in my chair. I expected to be suspended, or at least warned that I was facing disciplinary action or an investigation by the Independent Police Complaints Commission, but it was just coming up to seven when they let me go.

Seawoll offered me a lift, but I refused. I walked up St Martin’s Lane shaky with tension and lack of sleep. The weather had turned during the night. There was a chill wind under a dirty blue sky. The rush hour starts late on a Saturday, and the streets retained some of their early-morning quiet as I crossed New Oxford Street and headed for the Folly. I was expecting the worst, and I wasn’t disappointed. There was at least one unmarked police car that I could see parked across the street. I couldn’t see anyone inside, but I gave a little wave just in case.

I went in through the front door because it’s better to face things head on and I was too knackered to walk round to the mews at the back. I was expecting police, but what I got were a pair of soldiers in battledress and carrying service rifles. They wore woodland DP jackets and maroon berets with parachute regiment badges. Two were blocking my way past the cloakroom booths, while two more were tucked away either side of the main doors, ready to catch anyone suicidal enough to attack two fully armed paras in the flank. Somebody was taking the physical security of the Folly very seriously.

The paras didn’t raise their rifles to block me, but they did take on that air of menacing nonchalance that must have enlivened the streets of Belfast no end in the years before the peace agreement. One of them nodded his head towards the alcove where, in the Folly’s more elegant days, the doorman would wait until needed. Another para with sergeant’s stripes resided there with a mug of tea in one hand and a copy of the Daily Mail in the other. I recognised him. It was Frank Caffrey, Nightingale’s Fire Brigade liaison, and he gave me a friendly nod and beckoned me over. I checked the flashes on Frank’s shoulders. This was the 4th Battalion of the Parachute Regiment which I knew was part of the TA. Frank must have been a reservist, which certainly explained where he’d got the phosphorus grenades from. I suspected this was another part of the old boy network, but in this instance I was pretty sure that Frank was Nightingale’s boy. I didn’t see any officers around. I guessed they were back at the barracks turning a blind eye, while the NCOs sorted things out.

‘I can’t let you in,’ Frank said. ‘Not until your governor gets better, or they name an official replacement.’

‘On whose authority?’ I asked.

‘Oh, this is all part of the agreement,’ said Frank. ‘Nightingale and the regiment go back a way; you might say there were some debts.’

‘Ettersburg?’ I asked, guessing.

‘Some debts can never be repaid,’ said Frank. ‘And there are some jobs that have to be done.’

‘I have to get in,’ I said. ‘I need to use the library.’

‘Sorry son,’ he said. ‘The agreement is clear – no unauthorised access beyond the main perimeter.’

‘The main perimeter,’ I said. Frank was trying to tell me something, but sleep deprivation was making me stupid. He had to repeat himself before I realised that he was hinting that the garage was outside of the perimeter.

I stepped back out into the pale sunlight and made my way round to the garage and let myself in. There was a battered Renault Espace outside with such patently fraudulent plates that I knew it could only belong to the paratroopers. I took a moment to check that the Jag was locked before pulling a dust cover from under a workbench and throwing it over the vintage car. I tramped wearily up the stairs to the coach house, only to find that Tyburn had beaten me to it.

She was rummaging through the trunks and other old stuff that I’d piled at the far end. The picture of Molly and the portrait of the man I’d assumed was Nightingale’s dad were propped up against the wall. I watched as she knelt down and reached under the divan to pull out another trunk.

‘They used to call this a cabin trunk,’ she said, without turning round. ‘It’s made low enough to slide under your bed. That way you could pack the things you needed for your voyage separately.’

‘Or more likely your valet would,’ I said. ‘Or your maid.’

Tyburn lifted a carefully folded linen jacket from the cabin trunk and laid it on the divan. ‘Most people didn’t have servants,’ she said. ‘Most people made do.’ She found what she was looking for and stood up. She was wearing an elegant Italian black satin trouser suit and sensible black shoes. There was still a mark on her forehead where a marble fragment had cut her. She showed me her prize, a drab brown cardboard sleeve containing what I recognised as a 78rpm record. ‘Duke Ellington and Adelaide Hall, “Creole Love Call” on the original Black and Gold Victor label,’ she said. ‘And he has it stuffed in a trunk in the spare room.’

‘Are you going to sell it on eBay?’ I asked.

She gave me a cold look. ‘Are you here to pick up your things?’

‘If that’s all right with you?’

She hesitated. ‘Help yourself,’ she said.

‘You’re too kind,’ I said.

Most of my clothes were stuck in the Folly, but because Molly never cleaned the coach house I managed to scrounge a sweatshirt and a pair of jeans that had fallen behind the sofa. My laptop was where I’d left it, perched on a pile of magazines. I had to hunt around for the case. Tyburn kept her cool gaze on me the whole time. It was like being watched in the bath by your mother.

Sometimes, as Frank had pointed out, there are things you have to do no matter what the cost. I straightened and faced Tyburn. ‘Look,’ I said. ‘I’m sorry about the fountain.’

For a moment I thought it might work. I swear I saw something in her eyes, a softening, a recognition – something – but then it was gone, replaced by the same flat anger as before.

‘I’ve been investigating you,’ she said. ‘Your father’s a junkie, has been for thirty years.’

It shouldn’t hurt when people say these things to me. I’ve known my dad was an addict since I was twelve. He was quite matter-of-fact about it once I’d found out, and keen to make sure I understood what it meant – he didn’t want me following in his footsteps. He was one of the few people in the UK who still got his heroin on prescription, courtesy of a GP who was a big fan of London’s least successful jazz legend. He’s never been clean but he’s always been under control, and it shouldn’t hurt me when people call him a junkie, but of course it does.

‘Damn,’ I said. ‘He’s kept that really quiet. I’m shocked.’

‘Disappointment runs in your family, doesn’t it?’ she said. ‘Your chemistry teacher was so disappointed in you that he wrote a letter to the Guardian about it. You were his blue-eyed boy – figuratively speaking.’

‘I know,’ I said. ‘My dad keeps the clipping in his scrapbook.’

‘When they sack you for gross misconduct,’ said Tyburn, ‘will he keep that clipping as well?’

‘Deputy Assistant Commissioner Folsom,’ I said. ‘He’s your boy, isn’t he?’

Tyburn gave me a thin smile. ‘I like to keep track of the rising stars,’ she said.

‘Got him twisted around your little finger?’ I asked. ‘It’s amazing what people will do for a bit of slap and tickle.’

‘Grow up, Peter,’ said Tyburn. ‘This is about power and mutual self-interest. Just because you still do most of your thinking with your genitalia doesn’t mean everyone else does.’

‘I’m glad to hear that, because somebody has to tell him to trim those eyebrows,’ I said. ‘Did the gun come from you?’

‘Don’t be absurd,’ she said.

‘It’s your style. Get somebody else to solve your problems for you. Machiavelli would be proud.’

‘Have you ever read any Machiavelli?’ she asked. I hesitated and she drew the correct conclusions. ‘I have,’ she said. ‘In the original Italian.’

‘Why did you do that?’

‘For my degree,’ she said. ‘At St Hilda’s, Oxford. History and Italian.’

‘Double first, of course,’ I said.

‘Of course,’ she said. ‘So you understand why I don’t find Nightingale’s shabby gentility impressive in any way.’

‘So did you provide the gun?’ I asked.

‘No, I did not,’ she said. ‘I didn’t need to engineer this failure. It was only a matter of time before Nightingale screwed up. Although even I wasn’t expecting him to be stupid enough to get himself shot. Still, it’s an ill wind.’

‘Why aren’t you inside right now?’ I asked. ‘Why are you stuck in the coach house? It’s very impressive in there, got a library you wouldn’t believe and you could make a fortune hiring it out to film companies as a period location.’

‘All in good time,’ she said.

I fumbled my keys out of my pocket. ‘Here, I can lend you my keys,’ I said. ‘I’m sure you can talk your way past the paras.’ She turned away from my outstretched hand.

‘The one good thing to come out of this,’ she said, ‘is that now we get a chance to make a rational choice about how these matters are handled.’

‘You can’t go in,’ I said, ‘can you?’

I thought of Beverley Brook and her ‘inimical force fields.’

She gave me the Duchess look, the old money stare that footballers’ wives never get the knack of, and for a moment it rolled off her, the stink of the sewer and money and the deals done over brandy and cigars. Only, Tyburn being modern, there was a whiff of cappuccino and sun-dried tomatoes in there as well. ‘Have you got what you came for?’ she asked.

‘The TV’s mine,’ I said.

She said I could pick it up whenever I liked. ‘What did he see in you?’ she asked, and shook her head. ‘What makes you the keeper of the secret flame?’

I wondered what the hell the secret flame was. ‘Just lucky, I guess.’

She didn’t dignify that with a reply. She turned her back on me and returned to rummaging in the trunks. I wondered what she was really looking for.

On my way out through the coach yard I heard a muffled barking behind me and looked back. A pale, mournful face was watching me from a second-floor window – Molly, holding Toby tightly to her chest. I stood and gave them what I hoped was a reassuring wave, and then headed off to see if Nightingale was still alive.

There was an armed police officer stationed outside Nightingale’s room. I showed him my warrant card and he made me leave my bags outside. A modern ICU can be surprisingly quiet: the monitoring equipment only makes a noise when something goes wrong, and since Nightingale was breathing on his own there was no Darth Vader wheezing from a respirator.

He looked old and out of place among the polyester bed covers with their crisp, easy-to-clean pastel colours. One limp arm was exposed and hooked up to half a dozen wires and tubes, his face was drawn and grey and his eyes closed. But his breathing was strong, even and unaided. There was a bowl of grapes on the sideboard, and a bunch of blue wildflowers had been stuffed, a bit randomly I thought, into a vase.

I stood next to the bed for a while, thinking that I should say something but nothing came to mind. Checking first to make sure that no one was likely to see me I reached out and squeezed his hand – it was surprisingly warm. I thought I felt something, a vague sense of wet pine, wood smoke and canvas, but it was so faint I couldn’t tell whether it was vestigia or not. I caught myself swaying on my feet, I was that tired. There was an institutional armchair in the corner of the room. Made of laminated chipboard and polyester-covered fire-retardant foam, it looked far too uncomfortable to sleep in. I sat down, let my head flop to one side and was gone in less than thirty seconds.

I woke up briefly to find Dr Walid and a pair of nurses bustling around Nightingale’s bed. I stared at them stupidly until Dr Walid saw me and told me to go back to sleep – at least, I think that’s what he said.

I woke again to the smell of coffee. Dr Walid had brought me a cardboard jug of latte and enough tubular sachets of sugar to make a significant dent in my grocery budget.

‘How is he?’ I asked.

‘He was shot in the chest,’ said Dr Walid. ‘That sort of thing’s bound to slow you down.’

‘Is he going to be all right?’

‘He’s going to live,’ said Dr Walid. ‘But I can’t say whether he’ll make a full recovery or not. It’s a good sign that he’s breathing unaided, though.’

I sipped the latte; it burned my tongue.

‘They locked me out of the Folly,’ I said.

‘I know,’ said Dr Walid.

‘Can you get me back in?’

Dr Walid laughed. ‘Not me,’ he said. ‘I’m just a civilian advisor with a bit of esoteric expertise. With Nightingale incapacitated, unlocking the Folly is a decision that has to be made by the Commissioner, if not higher up.’

‘Home Secretary?’ I asked.

Dr Walid shrugged. ‘At the very least,’ he said. ‘Do you know what you’re going to do?’

‘Do you have access to the internet?’ I asked.

In a teaching hospital like UCH, if you walk through the right doors it stops being a hospital and becomes a medical research and administrative centre. Dr Walid had an office there and, I was shocked to learn, students. ‘I don’t teach them the esoteric stuff,’ he explained, but was – and not wanting to blow his own trumpet – a world-renowned gastroenterologist. ‘Everyone needs a hobby,’ he said.

‘Mine is going to be job-hunting,’ I said.

‘I’d have a shower first,’ said Dr Walid, ‘if you’re planning any interviews.’

Dr Walid’s office was an awkwardly narrow room with a window at the thin end and shelves covering the entire length of both long walls. Every surface was piled with folders, professional journals and reference books. At one end of the narrow shelf that served as a desk, a PC bobbed uncertainly in a sea of hard copy. I dumped my bags and plugged the laptop into the mains to recharge the batteries. The modem was hidden behind a stack of Gut: an International Journal of Gastroenterology and Hepatology. A jaunty subtitle revealed that Gut had indeed been voted Best Journal of Gastroenterology by gastroenterologists worldwide. I didn’t know whether to be worried or reassured by the implication that there were many more magazines devoted to the smooth functioning of my intestines. The socket for the modem looked suspiciously jury-rigged and definitely not standard NHS issue. When I asked Dr Walid about it, he merely said that he liked to keep certain of his files secure.

‘From who?’ I asked.

‘Other researchers,’ he said. ‘They’re always looking to pirate my work.’ Apparently the hepatologists were the worst. ‘What do you expect from people who deal with so much bile?’ said Dr Walid, and then looked disappointed that I didn’t get the joke.

Content that work was possible, I let Dr Walid show me to the staff bathroom down the corridor where I showered in a cubicle big enough, and equipped for, a paraplegic, his wheelchair, a care assistant and her guide dog. There was soap provided, a generic lemon-smelling antibiotic cake that felt ferocious enough to strip off the upper layer of my epidermis.

While I showered, I thought about the mechanics of how Nightingale got shot. Despite the lurid fantasies of the Daily Mail, you can’t just walk into a random pub and buy a handgun, especially not a high-end semiautomatic like the one carried so inexpertly by Christopher Pinkman the night before. Which meant that there was no way that Henry Pyke had manoeuvred Pinkman into place in the time between our arrival at the Royal Opera House and our emergence from the stage door less than twenty minutes later. Henry Pyke must have known that we were planning to trap him on Bow Street, and that left three options: either he foresaw the future, he read somebody’s mind or somebody who knew about the plan was one of his sequestrated puppets.

I dismissed precognition out of hand. Not only am I a big fan of causality, but Henry Pyke had never done anything else that suggested knowledge of the future. According to my research in the mundane library at the Folly, there was no such thing as mind-reading, at least, not in the sense of hearing someone’s thoughts as if they were narrating a voice-over on television. No: somebody had told Henry Pyke, or told somebody who was sequestrated by Henry Pyke, what the plan was. Nightingale didn’t. I didn’t. Which left the Murder Team. Given that Stephanopoulos and Seawoll were reluctant to talk about magic with its official practitioners, I couldn’t see them discussing it with their people, and Lesley would have followed their lead.

I stepped out of the shower feeling pleasantly raw, and dried myself off with a towel that had been repeatedly washed to the texture of sandpaper. The clothes I’d retrieved from the coach house weren’t exactly fresh, but at least they were cleaner than what I’d been wearing. After a few missed turnings in the featureless corridors I relocated Dr Walid’s office.

‘How’re you feeling?’ he asked.

‘Human,’ I said.

‘Close enough,’ he said. After that he pointed out the location of the coffee machine and left me to get on with it.

Ever since humankind stopped wandering around aimlessly and started cultivating its own food, society has been growing more complex. As soon as we stopped sleeping with our cousins and built walls, temples and a few decent nightclubs, society became too complex for any one person to grasp all at once, and thus bureaucracy was born. A bureaucracy breaks the complexity down into a series of interlocking systems. You don’t need to know how the systems fit together, or even what function your bit of the system has, you just perform your bit and the whole machine creaks on. The more diverse the functions performed by an organisation, the more complex the interlocking systems and subsystems become. If you are responsible, as the Metropolitan Police are, for preventing terrorist attacks, sorting out domestic rows and keeping motorists from killing random strangers, then your systems are very complex indeed.

One part of the system is the requirement that every OCU, that’s Operational Command Unit, has access to the HOLMES2 and CRIMINT databases either through a dedicated HOLMES suite or via specialised software installed on an authorised laptop. This is handled by the Directorate of Information who, because their responsibility is only to their bit of the system, don’t make a distinction between the Serious and Organised Crime Group (OCU) and the Folly, which was made an OCU only because nobody knew how else to drop it into the Met’s organisational chart. Now, this meant nothing to Inspector Nightingale, but to yours truly it meant that not only could I install a legal copy of the HOLMES2 interface into my laptop, but I was also provided with the same access privileges as the head of the Homicide and Serious Crime Command.

Which was just as well, because one of my suspects was Chief Inspector Seawoll, and that’s a target you don’t take aim at unless you’re certain it’s going to go down on the first hit. DS Stephanopoulos, who’d also known about the operation in advance, was an equally hard target, unless I wanted to be joke number two – Do you know what happened to the DC who accused Stephanopoulos of being the unwitting tool of a malicious revenant spirit? Dr Walid was suspect number four, which was why I didn’t tell him what I was up to; Lesley was suspect number five and suspect number six, the one that frightened me the most, was of course myself. There was no way of proving it, but I was reasonably certain that between killing William Skirmish and throwing his child out of the window, Brendan Coopertown had had no inkling that he was anything other than the same man he’d always been.

I hadn’t sensed anything from Lesley. Was it possible to mask a sequestration? Or, more likely, maybe I just wasn’t as sensitive as I thought I was. Nightingale was always telling me that learning to distinguishing vestigia from the vagaries of your own senses was a lifetime’s endeavour. I’d made an assumption about who was to be trusted – I wasn’t going to make the same mistake again.

After my shower I’d spent some time staring at my face in the mirror, working up the courage to open my mouth and look inside. In the end I closed my eyes and dug my fingers into my cheeks – I’ve never been so happy to fondle a bicuspid in my life. All that meant for certain is that Henry Pyke hadn’t stretched my face out yet.

I booted up HOLMES and typed in my access code and password. Technically both belonged to Inspector Nightingale and, technically, both should have been revoked as soon as he became inactive, but obviously nobody had got round to doing it yet – inertia being another key characteristic of civilisation and bureaucracy. I started at the beginning with the murder of William Skirmish, Covent Garden, 26 January.

I found what I was looking for three hours and two coffees later, when I was reviewing the Framline case. That attack had started with the cycle courier being knocked off his bike on the Strand and being taken to UCH for treatment, where he attacked Dr Framline. A uniformed PC had actually taken a statement from him at the scene of the accident while they were waiting for the ambulance to arrive. He’d claimed that a driver had overtaken him and deliberately forced him off the road. Lesley had told me that the accident had taken place in a rare CCTV blind spot on the Strand, but according to the initial report, the courier had been forced off the road outside Charing Cross Station. There hasn’t been a camera blind spot outside a London rail terminus since the IRA declared them legitimate targets in the 1990s. I went rummaging in the bowels of the HOLMES archive, where some demented soul on the Murder Team had uploaded the relevant footage from every single operable camera from Trafalgar Square to the Old Bailey. None of it was labelled properly, and it took me a good hour and a half to find the video I was looking for. The cycle courier hadn’t specified what make of car had crowded him, but there was no mistaking the battered Honda Accord that deliberately ran him off the road. The video resolution wasn’t good enough to show the driver or the licence plate, but even before I tracked its progress to the high-resolution traffic camera that guarded the lights at Trafalgar Square, I knew who it belonged to.

It made sense. She’d been present when Coopertown killed his wife and child, during the incident in the cinema and the attack on Dr Framline. She’d been there when we planned the operation outside the Opera House, and she’d arrived with the back-up in time to pick up the missing pistol.

Lesley May was my suspect. She was part of it, sequestrated by Henry Pyke as part of his mad play of riot and revenge. I wondered if she’d been part of it from the beginning, from the first night when William Skirmish had his head knocked off and I’d met Nicholas Wall-penny. Then I remembered Pretty Polly from the Piccini script – the silent girl romanced by Punch after he’d killed his wife and child. He kisses her most audibly while she appears ‘nothing loath’. Then he sings, If I had all the wives of old King Sol, I would kill them all for my Pretty Poll.

There was a mother who lost her son in Covent Garden once. She was very English in an old-fashioned way, good-quality print dress, nice bag, down for a shopping trip to the West End and a visit to the London Transport Museum. Got distracted by a window display for a moment and turned back to find her six-year-old boy had gone.

I remember very clearly how she looked by the time she found us. A surface veneer of calm, a traditional British stiff upper lip but her eyes gave her away – darting left and right, she was fighting the impulse to run in all directions at once. I tried to keep her calm while Lesley called it in and started organising a search. I don’t know what I was saying, just calming words, but even while I was speaking I saw that she was shaking almost imperceptibly, and I realised that I was watching a human being come apart in front of my eyes. The six-year-old turned up less than a minute later, led up from one of the Piazza’s sunken courtyards by a kindly mime. I was looking right at the mother when the son reappeared, saw the relief laid bare on her face and the way the fear was sucked backwards into her until only the brisk and practical woman in the sundress and the sensible sandals remained.

Now I understood that fear, not for yourself but for somebody else. Lesley had been sequestrated – Henry Pyke was sitting in her head and had been there for at least three months. I tried to remember the last time I’d seen her. Had her face looked different? And then I remembered her smile, the big grin showing lots of teeth. Had she smiled at me recently? I thought she might have. If Henry Pyke had activated the dissimulo on her, made her over into Pulcinella’s form, there’s no way she could have disguised the ruin of her teeth. I didn’t know how to get Henry Pyke out of her head, but if I could get to her before the revenant made her face fall off then I thought I might know how to stop that, at least.

By the time Dr Walid returned to his office, I had a plan.

‘What is it?’ he asked.

I told him, and he thought it was a terrible plan as well.