But then the answer came stalking down the street towards me, the cynosure of all eyes - I counted six, including mine, the other sets belonging to a homeless guy and a roosting pigeon on a window ledge. All the same, she walked like a queen in procession, the night unrolling its monochrome carpet before her.

I detached myself from the doorway and waved, but Juliet had seen me already. Of course she had: her eyes were adapted for much darker places than this. They had the same faint glow to them that I’d noticed back at the Gaumont. More unsettlingly, the proportions of her body looked subtly different. She was taller, leaner, longer-limbed, without being any less beautiful, any less perfect. She was dressed in red rather than her usual black, and it was shocking to look at, the leather jacket shining with a liquid gloss, as vivid as an open wound, the pleated skirt infolded like labia.

‘Thanks for coming,’ I said when she was in earshot.

‘You piqued my curiosity,’ she answered. ‘Show me this thing. But you’d better not let me down, Castor. I don’t like men who make promises and can’t deliver.’ The shape of her face had changed too. It had elongated and thinned, the cheekbones becoming higher and sharper. The overall effect was to make her look less human, or rather to make her humanity seem like more of a conscious affectation. Her body had become an ironic quote.

‘I’m as good as my word,’ I promised her, trying to make my voice resonate with a confidence I really didn’t feel. ‘I said I’d show you something new, and I’m going to. But anyway, you’re still on my payroll, right? Still on demon watch. I was hoping you could give me an update on that.’

Juliet tilted her head back very slightly, her red eyes fixed on me like rangefinders. ‘You want to make sure you’re getting your money’s worth?’ she translated, with a dangerous edge of anger in her voice.

‘I want to make sure nothing happened to Pen while I was away,’ I said. ‘Or to you. That’s all.’

‘I haven’t seen Asmodeus, or felt him. If he’s watching your house, or the woman, he’s doing it from a distance. Circumspectly. Patiently. Does that sound like Asmodeus to you?’

It didn’t, I had to admit. On the other hand, he’s the kind of devious bastard who gives devious bastards a bad name. ‘You know what they say about barn owls?’ I asked her.

Juliet stared at me as though I was something she’d found crawling in her armpit. ‘No, Castor. I don’t know what they say about barn owls.’

‘They call twice when they’re hunting - the first time loud, the second time soft. It puts the prey off its guard. Makes it sound like they’re heading away from you when they’re about to drop out of the sky and put their claws through your eye sockets.’

‘The “you” in this sentence being a mouse or a rabbit,’ Juliet observed with cold amusement. ‘I don’t find it easy to identify with prey, Castor. It’s interesting that you do. Now, given that you could have asked me these questions by phone and not disturbed my sleep, why am I here?’

There was a pause - barely perceptible - before the word ‘sleep’. It made me hope that relations between Juliet and Sue might have improved somewhat, but since I’ve got a well-developed sense of self-preservation I didn’t ask. ‘Come and see,’ I said.

The invitation had an unintentionally biblical ring. Wasn’t that what the angel said to John when the Book of Revelation was opened? Thinking of apocalypses, I unlocked Super-Self’s front door and stood aside for Juliet to enter.

Super-Self felt different tonight. Juliet stepped inside, casting her gaze to right and left. She opened her mouth and stuck out her tongue to taste the air.

‘Nothing,’ she said at last, her vivid red eyes narrowing slightly.

‘We’re not there yet,’ I said.

I walked past her to the stairs, expecting to hear after a moment or two the clack of her heels as she fell in behind me. Nothing. Despite the stiletto heels of her blood-red shoes, she walked as silently as a cat. I knew she was there, because she was a radarblip in my awakened death-sense, and the back of my neck prickled from the near-physical pressure of her stare. Otherwise I would have felt like Orpheus. Orpheus on the downward leg of the journey, heading into Hades on a busker’s prayer.

The reception area was silent and pitch black. I went to turn on the lights, but Juliet’s hand blocked mine. ‘Hurts my eyes,’ she murmured absently.

‘I can’t see in the dark,’ I pointed out.

‘You’ll adjust.’

She was right. There was a little light filtering down the stairs - the street lamps shining in through Super-Self’s open doors. It wasn’t much, but it was enough to show me the outlines of objects. Paradoxically, despite the vivid scarlet tones of her outfit, now Juliet was darker than the darkness, a silhouette against solid black. Even her eyes had stopped glowing, as though their light had shifted into a part of the spectrum I couldn’t see.

‘Show me this thing,’ she said again. The playfulness in her tone was the most terrifying thing I’d ever heard.

Moving slowly to avoid falling over any low-lying items of furniture, I crossed the dark space to the far door, which opened not onto the pool but onto its anteroom.

I put my hand to the door, bracing myself for what was on the other side. I was a little surprised that I hadn’t felt it already, but perhaps this was how it worked: sitting like a spider in a web, dormant, almost asleep, until something touched one of the threads and woke it.

Juliet pushed me aside impatiently and walked into the anteroom ahead of me. There was more light here: the phosphorescence from the pool beyond cast shifting blue highlights onto the walls. Juliet tilted her head back, seeming to listen, but there was no sound except the arrhythmic lapping of the water against the tiles.

‘If we go a little closer—’ I began. Juliet made a brusque gesture, silencing me.

‘Yes,’ she murmured at last, her voice husky. Her lips peeled back from her teeth in a feral grin. ‘That’s what it wants. Go on, Castor. Move in closer.’

I hesitated. Juliet’s mood was hard to read, but those bared teeth were unsettling. I was suddenly more afraid of her than I was of the thing in the swimming pool beyond.

‘Closer,’ she said again. ‘It won’t show itself until you do. It’s hidden itself, used the souls of the dead to break up its outline. I won’t see it clearly until it moves, and it won’t move unless we throw out some bait. I’ll be right behind you.’

Yeah, that was very reassuring.

I went on through the arch to the water’s edge. The moving lights below me resolved themselves again into human shapes - became men and women in the depths of the water, circling and gesturing in an endless dumb show. At that moment I felt an aching solidarity with them. They’d lived and breathed once, been fully human, unlike either the thing that crouched invisible in the darkness above me or the siren at my back.

I leaned forward to see better. There were fewer figures in the pool than I remembered from the night before - seven or eight, where my confused memories had conjured up a crowd of several dozen. The two men in togas were arguing - one calmly, the other with a lot of emphatic gestures and striding back and forth. Another, older man watched them, majestically detached, while two women stood off to one side with their faces averted, looking sad and afraid. Two Roman soldiers with breastplates and helmets stared straight ahead, patient and impassive.

One of the women put her hand to her face. Something clutched in her fist caught my eye, and I leaned forward to see it more clearly. That was when the fear-thing fell on me like the giant foot in a Monty Python sketch. The last time I was here the process had been more gradual: an inexplicable sense of unease in the hall above, creeping paranoia on the stairs, pure, pants-wetting terror at the poolside. This was different. It was like having my brain ripped out of my skull and dropped into liquid nitrogen while it was still bleeding and pulsating.

Thought was impossible. So was movement. Fuck, so was breathing. My chest locked up as though all my ribs had twanged free and got tangled up together like one of Trudie’s cat’s cradles.

Poleaxed, and already off balance, I toppled forward into the water. I didn’t hear the splash even, but my eyes were open and I could still see as I sank down among the ghosts. They ignored me completely, playing out their pantomime around and through me in the blue-white spotlight created by their own phosphorescence.

For a moment I was staring into the face of the woman I’d been watching from above. It was a tragic face, eyes pleading and haunted, mouth tensed in a just-about-to-lose-it grimace. But I kept on sinking down and down. Now I was level with her shoulders, her chest, her arms. Her hand clutched tight around the flimsy thing she’d drawn out from the voluminous folds of her gown. It was a lace handkerchief, embroidered with the letters EC in elegant - if slightly over-elaborate - needlepoint.

Water was starting to trickle into my mouth, down my throat. Since I wasn’t breathing, it hadn’t found my airway yet, but it wouldn’t be long.

In the meantime, as my shoulder bumped against the bottom of the pool, I’d noticed that the woman’s shoes were wrong too: they were low boots made of leather, with scrimshaw buttons up the side. God damn it, she was even wearing socks.

Still unable to move a voluntary muscle, I turned slowly in the water, rolling over onto my back. The trickle of water became a torrent, and I cursed my luck silently as I prepared to say goodbye to the world.

Then something locked hard onto my ankle and hauled me upward like a hooked fish. I exploded out of the water into the cool night air, and the shock of the cold and the sudden movement started me breathing again. Okay, I was breathing water: a small detail, easily adjusted once I’d coughed and hacked and vomited myself back into equilibrium.

Juliet dumped me on the tiles without ceremony and left me to it. When I was in a state to take notice of her again, she was staring up into the light well above the pool, her knees slightly bent as though she was ready to spring. But the fear had gone - gone completely, in an instant, just as it had arrived. I was about to listen in through my death-sense to confirm my conviction that we were alone, but I stopped myself just in time. That was how the damn thing worked. That was what it responded to.

Yesterday, when I’d come here with Trudie, the pair of us had come through the door on a hair trigger, knowing - because we’d been told - that this was a woodshed with something nasty in it. We were tuned into the psychic wavelengths, using the sensitivities that made us exorcists, and the fear-thing had woken up instantly. We’d started to feel it as soon as we crossed the threshold.

Tonight, I’d let Juliet take the lead and make the running, wanting her to see for herself. My death-sense hadn’t stirred until I looked down into the pool and focused on the ghosts and what they were doing. That was when the fear-thing had pounced.

And that was why the bad shit just kept on escalating. The more exorcists Jenna-Jane sent in here, the harder she poked this thing, the harder it hit back.

I came up on one knee, groggy and hurting. Juliet hadn’t put me down any too gently, and there was an ache all the way up my right forearm and shoulder, but it felt great just to be able to think straight.

‘Did you see it?’ I asked her.

She looked down at me, seeming slightly surprised that I was still there. ‘Of course I saw it.’

‘So tell me what it is,’ I persisted.

‘Tartharuch,’ Juliet growled, her mouth twisting around the gutturals. ‘From Tartarus. Tartharuch Gader’el.’ She was still staring at me, her eyes hot coals in the darkness.

‘So it’s a demon.’

‘Yes. It’s a demon.’

‘And how do we kill it?’

‘Kill it?’ Juliet’s flawless brow furrowed. ‘Why would I want to kill it? It smells of home.’

Something in the set of her mouth rang alarm bells in my mind. They were still vibrating anyway from my second round with the fear-thing, the Gader’el, so it didn’t take much to set them off. I started to climb to my feet.

I didn’t even see Juliet move. Something - her fist or her foot, I couldn’t be sure - hit me in the middle of my chest and knocked me sprawling. Then she was on top of me, her face about an inch from mine. She licked her lips and my heart surged, clamouring like a monkey in a cage. Her sex scent filled me in a second to bursting point, the way a water balloon held against a running tap is filled, distends and then explodes.

I tried to speak. ‘This . . . this is . . .’ Her parted lips, impossibly full and dark, were descending towards mine. It seemed like a waste of time talking when I could just give myself up to those lips and the terrible release they promised. But I’d been here once before, on Juliet’s event horizon, and survived. Clawing for purchase on that memory, some part of me was able to grab a microscopic distance from the agonising, all-consuming lust and remind me that I was about to die. ‘Bad idea,’ I forced out. ‘Sue . . .’

Juliet hesitated. A wave of some very human emotion - irritation, impatience, something like that - passed across her face, displacing for a moment the wanton mask she wore when she was hunting. I have no idea what had risen in her mind: the echo of an old argument maybe, a domestic quarrel between her and her human lover in the early, honeymoon days, about the ethics of devouring the odd guy on the side when you’re in a monogamous relationship.

Whatever it was, it gave me a window. I whistled into it: whistled Juliet. It was desperate improvisation. I couldn’t think around her, couldn’t pull myself out of her orbit, but as an exorcist I could put what I was feeling to good use. It was the summoning, the first phase of an exorcism, when you make the spirit you’re binding stand to attention and pay heed to you. I called Juliet back into herself, as I’d done for her once before after she fought Moloch at the Mount Grace Crematorium, and as I’d tried and failed to do for Lisa Probert.

Dumb luck counts for a lot in my business. Doing that gave me my second big insight of the night, the first one being when I looked at the lace handkerchief in the Roman matron’s hand and realised she wasn’t Roman at all. What I realised now was that Juliet was all wrong. There was a mismatch, a discord, between what I was playing and what I was feeling - between the Juliet I knew, whose soul-music I’d memorised by heart, and the Juliet who was crouched above me now preparing to devour me. They weren’t the same being. They overlapped, but they weren’t the same.

If I’d had time to think about the implications of that, I might have got the answer there and then, and everything that happened later might have played out differently. But the moment wasn’t really conducive to calm reflection. Juliet’s pheromones still saturated the air, my heart was still trying to start up a new career as a road drill, and it took all my effort, all my concentration, just to keep forcing that tune out between my pursed lips.

We must have stayed like that for the best part of a minute, a tableau from a Benny Hill sketch. Then Juliet leaned back, shifting her weight, and made a gesture with her right hand: stop. Seeing her hand from so close up, I noticed again that it was too long, the fingers impossibly tapered. Physically as well as psychically, Juliet was in a state of flux.

She climbed off me. It hurt to be released from that weight, to feel her attention pass over me and shift away. I’d survived her attack again, and just like the first time it was agonising. My maddened hormones threshed in my innards like waves against a breakwater, and a fevered tremor went through me, leaving me breathless and weak. My teeth chattered out a crazy, Morse code lament. It was like the alcohol craving all over again, but worse.

Juliet hauled me to my feet without apparent effort even though I wasn’t able to contribute much to the process. She propped me against the side of the arch, looking me up and down with an abstracted frown, inspecting me for damage maybe.

‘Told you . . . a long time ago . . .’ I panted, ‘I wasn’t that kind of boy.’

‘Shut up, Castor.’ Juliet seemed to be her old self again, or something close to her old self, but it hadn’t improved her mood. Still, it shortened the odds on a meaningful dialogue.

‘Tell me what happened,’ I threw at her. ‘Explain to me what just happened.’

She took her hand away from my shoulder to see if I’d fall down again. I didn’t. Satisfied, she walked back to the edge of the pool and stared up into the grey void of the light well.

‘I lost control,’ she said at last.

‘You seem to have been doing that a lot lately.’

‘Yes.’

‘Any idea why?’

She took on that attentive stance again, shoulders rigid, head tilted slightly back. She was feeling for the presence of the fear-thing. Bearing in mind what had happened when she made contact a few minutes ago, I wasn’t thrilled with the idea of sitting around and letting the two of them cuddle up some more.

‘Juliet,’ I called.

With visible reluctance, she turned and faced me.

‘Did this thing - this Tartarus whatever-it-is - do something to your mind?’

She gave a brief, harsh laugh. ‘The Gader’el? No, Castor. It’s just an animal.’

‘An animal?’

‘An animal from Hell. It’s dangerous, to the unwary, and hard to eradicate, but it can’t think. Its repertoire is just what you see here: it hides itself, and it strikes while your back is turned. It feeds on fear, in the same way that I feed on lust or the Shedim feed on the souls of murderers.’

I rubbed my bruised shoulder. ‘Then what?’ I said. ‘What the fuck is happening to you?’

She stared at me in silence. She was just a silhouette now, because the ghosts in the pool had gone and the blue light had died, but the red fires in Juliet’s eyes told me I had her attention and that she wasn’t entirely the Juliet I knew and sexually obsessed about, even now.

‘I don’t know,’ she admitted. She seemed to pull herself together. ‘We should leave. I startled the Gader’el, and interrupted its feeding. If it comes back again, it will be bolder.’

‘Why should it come back?’ I asked.

Juliet smiled a bleak, humourless smile. ‘Because you’re scared of me, Castor. Why else?’

On the pavement outside she made to walk away, but I reached out and caught her shoulder. It was a symbolic thing: light and slender as she was, she was as strong as ever, and she could have broken my grip without trying. She half-turned, waiting for me to speak.

‘Go home,’ I said. ‘Promise me you’ll go home.’

Silence.

‘Juliet, you can’t hunt tonight. I can’t let you.’

‘You can’t stop me,’ she said with dead finality.

‘I know,’ I acknowledged. ‘So give me a break, and don’t make me die trying. Go home to Sue. Have a quiet night in. Remind yourself what you’ve got to lose.’

‘Fuck you, Castor.’

‘Again?’ I made my tone astonished and outraged. ‘Are you insatiable, woman?’

In spite of herself, she laughed. But the feeble joke was a challenge too, and the word ‘woman’ gave her the benefit of the doubt.

‘I’ll go home,’ she agreed. ‘But tomorrow . . .’

‘Tomorrow we’ll figure something out.’

She nodded without conviction. Then she turned her back and walked away from me down the Strand. A staggering cluster of drunks on the opposite side of the street shouted out some sort of sleazy invitation to her, and I tensed, ready to intervene if necessary. But Juliet didn’t even seem to see them. Head down and shoulders squared, she marched on into the hot, breathless night.

I didn’t see or sense any sign of the demon’s presence, or any clue that he’d been there while I was away. In another way though, I felt myself surrounded and crowded by him. What he was doing wasn’t random - I knew that much. Behind the casual malevolence there was something much more calculating and purposeful, and much more threatening.

I let myself in quietly. I heard voices from downstairs, Pen’s basement sanctum, which surprised me, but only until I heard the laugh track. She’d fallen asleep in front of a repeat of some ancient sitcom, snoring away on the sofa while Reg Varney and Michael Robbins traded accusations of sexual dysfunction without ever using the word ‘penis’. I sat down next to her and stared at the screen while the flaccid shenanigans played themselves out. In a way it helped me to think, if only because thinking distracted me from On the Buses.

There was a way through this maze. It just meant figuring out where Asmodeus was going so I could get there first. Of course, I also had to get myself a secret weapon to use when I got there, because a tin whistle wasn’t going to do the job. It hadn’t even been enough to beat the Gader’el, which Juliet had dismissed as an animal.

The trouble was that you couldn’t get close enough to the Gader’el to perform an exorcism. I had its pattern clear in my mind now, but I knew damn well that as soon as I started to play, it would be on me hard enough and fast enough to knock the tune right out of my head. Close enough to play meant close enough to be attacked.

Inspiration came out of nowhere. No, it came out of thinking about Trudie, and the way she’d bootstrapped her own MO to create the meta-map of Asmodeus’ movements. The trick was seeing through the metaphor to the thing itself: distinguishing how your power actually worked from the interface you’d developed for it. It could be done. It could be done without risk even.

That solved Jenna-Jane’s problem. Now what about mine?

‘Fix.’ Pen stirred on the sofa beside me, rubbing her eyes. ‘What time is it?’

I didn’t bother to check my watch. ‘Later than you think,’ I said. ‘Like always. How was your day?’

She blinked and shook her head, restoring some shape to the incendiary mop of her hair. ‘Wonderful,’ she said, her voice husky and slurred with sleep. ‘Like one of your days. Alcohol, self-hatred, more alcohol and daytime TV.’

‘I don’t watch that much TV,’ I pointed out. ‘What do you hate yourself for?’

‘Just the obvious.’ She sat up, still groggy but gradually coming awake. ‘I can’t do this, Fix. I can’t sit here and wait for you to sort it out. I’m going to start looking for Rafi again tomorrow.’

‘You won’t find Rafi;’ I reminded her, my voice hard, ‘you’ll find Asmodeus.’

‘I don’t care. This isn’t any way to live.’

She was right. We were under siege, and it was affecting both of us in our different ways. The sense of pressure - the feeling of being stalked - was throwing me off my stride, so that I just kept running from one thing to the next instead of stopping to think about where I was going. Worse, I was letting Jenna-Jane set the agenda, when I should have been using her as she was using me: bouncing off her thick, impervious hide in the direction I most needed to go.

That was going to change.

Right now I was going to get some sleep. And in the morning, which was only two and a half hours away . . .

In the morning I was taking back the initiative.