'I have a special assignment. You can direct your enquiry to my superiors. Or rather, you have the right to address your enquiry to your superiors.'

The witch and the warlock exchanged glances. No matter how opposed our goals and moralities might be, the two hierarchies had to collaborate.

Only, to be quite frank, nobody really liked involving the bosses.

'Very well,' the witch agreed reluctantly. 'Anton, we will limit ourselves to a verbal warning.'

I looked around. All round me there were people, moving slowly through the grey gloom. Ordinary people, incapable of moving out of their own little world. We were Others, and though I stood on the Light Side and the other two were on the Dark Side, we had far more in common with each other than with any of those ordinary humans.

'On what terms?'

You should never try to second-guess the Dark. You should never make any concessions. And it's even more dangerous to accept any gifts from it. But rules are only made to be broken.

'No terms.'

Well, that was a surprise!

I looked at Alisa, trying to figure out the catch. Pyotr was obviously indignant at his partner, he was angry, he wanted to expose an adept of the Light as a criminal. That meant I didn't have to worry about him.

But where was the trap?

'That's unacceptable to me,' I said, with a sigh of relief – I'd spotted the catch. 'Alisa, thank you for your offer of a peaceful resolution. I can accept it, but in a similar situation I am bound to forgive you a minor magical intervention, up to and including the seventh degree.'

'Very well, Other,' Alisa agreed readily. She held out her hand and I automatically shook it. 'We have a personal agreement.'

The owl on my shoulder flapped its wings. There was a furious screech right in my ear. And a moment later the bird materialised in the Twilight world.

Alisa took a step back and the pupils of her eyes rapidly extended into vertical slits. The young warlock took up a defensive stance.

'We have an agreement,' the witch repeated sullenly.

What was going on?

I realised too late that I shouldn't have entered into an agreement while Olga was there. But then – what was so terrible about what had happened? As if I hadn't been there when other guys from the Watch had concluded alliances like this, made concessions, agreed terms for co-operating with the Dark Ones, even the boss himself had done it! Sure, it's undesirable, but sometimes you have to.

Our goal is not to exterminate the Dark Ones. Our goal is to maintain the balance. The Dark Ones will only disappear when people conquer the Evil in themselves. Or we'll disappear, if people decide they like the Dark better than the Light.

'The agreement's been made,' I told the owl. 'Cool it. It's no big deal. Just standard collaboration.'

Alisa smiled and gave me a wave. She took the warlock by the elbow, and they started moving off. A few moments later they were out of the Twilight and setting off along the pavement. An ordinary young couple.

'What's wrong with you?' I asked. 'Well? Field work has always been built on compromises.'

'You made a mistake.'

Olga's voice was strange, it didn't match her appearance. Soft, velvety, musical. The way werecats talk, not birds.

'Oh! So you can talk now?'

'Yes.'

'Then why didn't you say anything before?'

'Everything was okay before.'

I laughed, remembering the old joke about the child that didn't speak for years.

'I'll leave the Twilight, okay? And meanwhile you can explain what mistake I've made. Minor compromises with the Dark Ones are inevitable in this line of work.'

'You're not well enough qualified to make compromises.'

The world around me became coloured. It was like switching modes on a video camera, when you change from 'sepia' or 'old movie' to the standard view. The comparison is really quite apt in some ways: the Twilight is an 'old movie'. A really old one that humankind has managed to forget. They find it easier to live that way.

I set off towards the steps down into the metro, snarling to my invisible companion on the way:

'And just what have qualifications got to do with it?'

'A high-ranking Watch member is able to foresee the consequences of a compromise. Whether it's no more than just a minor trade-off and the effects are self-neutralising, or a trap, a trick.'

'I doubt if a seventh-grade intervention's likely to lead to disaster.'

A man walking along beside me glanced at me in surprise. I was just about to say something like: 'I'm harmless, the non-violent kind of psycho.' It's a great way of curing excessive curiosity. But the man had already lengthened his stride, probably having come to a similar conclusion himself.

'Anton, you can't predict the consequences. You overreacted to a minor annoyance. Your little piece of magic led to intervention by the Dark Ones. You agreed a compromise with them. But the saddest thing of all is that there was no need for magical intervention in the first place.'

'Okay, okay, I admit it. So now what?'

The bird's voice was sounding more lifelike now, developing more expression.

I suppose it must have been a long time since she'd last spoken.

'Now – nothing. We'll have to hope for the best.'

'Are you going to tell the boss what happened?'

'No. At least, not yet. We're partners, after all.'

I felt a warm glow. This sudden improvement in relations with my partner made any mistakes worthwhile.

'Thanks. So what do you advise?'

'You're doing everything right. Look for the trail.'

I'd have preferred rather less standard advice . . .

'Let's go.'

By two o'clock, along with the circle line, I'd combed the entire grey line too. Maybe I am a lousy operational agent, but there was no way I could have failed to spot the trail from yesterday, when I'd captured the image myself. The girl with the black vortex spinning over her head hadn't got out here. I'd have to go back and start again from the point where we'd met.

At Kurskaya I went up the escalator and out of the metro and bought a plastic tub of salad and a coffee from a van on the street. The very sight of the hamburgers and sausages made me feel sick, even though the amount of meat in them was strictly symbolic.

'Will you have something?' I asked my invisible companion.

'No, thank you.'

Standing there with the fine snow falling on me, I picked at my salad with a tiny plastic fork and sipped the hot coffee. A bum who'd been counting on me buying a beer, so that he could have the empty bottle, hung about for a bit and then took off into the metro to get warm. Nobody else paid any attention to me. The girl behind the counter served the hungry passers-by, faceless streams of people flooded from the station and back towards it. The salesman at a bookstall was trying wearily and unenthusiastically to foist some book or other on a customer, who didn't like the price.

'I must be in a bad mood or something . . .' I muttered.

'Why?'

'Everything looks dark and miserable. All the people are low-lifes and idiots, the salad's frozen, my boots feel damp.'

The bird on my shoulder screeched.

'No, Anton, it's not just your mood. You can sense the approach of the Inferno.'

'I'm not noted for being particularly sensitive.'

'That's just the point.'

I glanced at the station and tried to get a close look at people's faces. Some of them were sensing it too. The ones who stood right on the line between human and Other were tense and depressed. They couldn't understand why, so they were compensating by acting cheerful.

'Dark and Light. . . What will it be when it happens, Olga?'

'Anything at all. You delayed the time of the eruption, but now when the vortex strikes the consequences will be absolutely catastrophic. That's the effect of delay.'

'The boss didn't tell me that.'

'Why should he? You did the right thing. Now at least there's a chance.'

'Olga, how old are you?' I asked. Between humans the question might have been taken as an insult. But for us age doesn't have any particular limits.

'Very old, Anton. For instance, I can remember the uprising.'

'The revolution?'

'The uprising on Senate Square, in 1825.' The owl chortled. I didn't say anything. She could be even older than the boss.

'What's your rank?' I asked.

'I don't have one. I was stripped of all rights.'

'I'm sorry.'

'No problem. I came to terms with it a long time ago.'

Her voice was still cheerful, even mocking. But something told me Olga had never come to terms with it.

'If you don't mind me asking . . . Why did they shut you in that body?'

'There was no other option. Living in a wolf's body is much harder.'

'Wait . . .' I dropped the remains of the salad in a bin. I looked at my shoulder, but, of course, I didn't see the owl – to do that I would have had to withdraw into the Twilight. 'What are you? If you're a shape-shifter, then why are you with us? If you're a magician, then why such an unusual punishment?'

'That's got nothing to do with the job, Anton.' For just a moment there was a hint of steel in her voice. 'But it all started with me compromising with the Dark Ones. Only a small compromise. I thought I'd calculated the consequences, but I was wrong.'

So that was it . . .

'Was that why you started talking? You wanted to warn me off, but you were too late?'

No answer.

As if Olga was already regretting being so frank.

'Let's get on with the job,' I said. And just then the phone buzzed in my pocket.

It was Larissa. What was she doing working two straight shifts?

'Anton, listen carefully . . . They've picked up that girl's trail. Perovo station.'

'Shit,' was all I said. Working the commuter suburbs was hell.

'Right,' Larissa agreed. She was no field operative . . . that was probably why she was sitting by the phone. But she was a bright girl. 'Anton, get over to Perovo. All our team are concentrating over there, they're following the trail. And another thing . . . they've spotted the Day Watch there.'

'I get the picture.' I folded away my phone.

I didn't get it. Did the Dark Ones already know everything? Were they just yearning for the Inferno to erupt? Then maybe it was no accident that they'd stopped me?

Rubbish. A major disaster in Moscow was hardly in the interests of the Dark. But of course, they wouldn't try to stop the twister either: that would be to go against their nature.

So I didn't go by metro after all. I stopped a car. It ought to save me a bit of time, even if not much. I sat beside the driver, a swarthy intellectual about forty years old. The car was new, and the driver gave the impression of doing very well for himself. It seemed a bit odd for him to be earning a bit on the side by offering a taxi service.