When Egor passed me my tea, I tipped five heaped spoons of sugar into the mug and winked at him.

'Pour me a glass of tea with two spoons of sugar ... I want to try it before I die.'

He obviously didn't know that old joke.

'And how many should I take?' he asked.

'How much do you weigh?'

'I don't remember.'

I estimated his weight by eye.

'Put four in. To prevent hypoglycaemia.'

Gulping down his tea, he said:

'Explain!'

This wasn't anything like the way I'd planned. Follow the boy when the Call reaches him. Kill or capture the vampire. And take the grateful boy to the boss – he'd be able to explain everything properly.

'Once upon a time . . .' I said. 'Like the beginning of a fairy tale, that, isn't it? Only this isn't a fairy tale.'

'I'm listening.'

'Okay. I'll start with something else. There is a human world.' I nodded towards the window, the little courtyard outside and the cars crawling along the road. 'There it is. All around us. And most people can't move beyond it. That's the way it's always been. But sometimes we turn up. The Others.'

'And vampires?'

'Vampires are Others too. They're a different kind of Other, though, their powers are determined in advance.'

'I don't understand,' said Egor, shaking his head.

Okay, so I'm no tutor. I'm no good at expounding the basic truths, I don't enjoy it . . .

'Imagine two shamans who have gorged themselves on narcotic mushrooms, beating on their tambourines,' I said. 'A long, long time ago, back in prehistoric times. One of the shamans is putting one over on the hunters and the chief. The other one suddenly sees his shadow, which was trembling on the floor of the cave, gain volume and rise up until it stands erect. He takes a step forward and enters the shadow. He enters the Twilight. And that's when the most interesting part begins. You understand?'

Egor didn't say anything.

'The Twilight changes the person who has entered it. It's a different world, and it makes people into Others. But who you become depends entirely on you. The Twilight is a raging river flowing in all directions at once. Decide who you want to be in the Twilight world. But make up your mind quickly, you don't have much time.'

Now the boy understood. His pupils contracted and his skin turned slightly paler. An excellent stress response, he really would make a good operational agent. . .

'Who can I become?'

'You? Anybody you like. Your choice still hasn't been made. And you know what the basic choice is? Good or Evil. Light or Dark.'

'And are you Good?'

'First and foremost I'm an Other. The difference between Good and Evil lies in your attitude towards ordinary people. If you choose the Light, you won't use your powers for personal gain. If you choose the Dark, that will be what you do most of the time. But even a black magician is capable of healing people and finding people who have been lost. And a white magician can refuse to help people.'

'Then I don't see what the difference is.'

'You will. You'll understand when you choose one side or the other.'

'I'll never choose!'

'It's too late, Egor. You've already been in the Twilight, and you're already changing. In a couple of days the choice will have been made.'

'If you choose the Light . . .' Egor got up and poured himself some more tea. I noticed it was the first time he hadn't been afraid to turn his back on me. 'Then who are you? A magician?'

'A magician's apprentice. I work in the office of the Night Watch. Someone has to.'

'And what can you do? Show me, I want to see.'

There it was, straight out of the textbook. He'd been in the Twilight, but that hadn't convinced him. Petty fairground tricks are far more impressive.

'Watch.'

I held my arm out towards him. Egor froze, trying to understand what was going on. Then he looked at his cup.

The steam had stopped rising from his tea. The tea was crackling as it turned into a cylinder of muddy brown ice with tea leaves frozen into it.

'Oh,' said the boy.

Thermodynamics is the simple part of manipulating matter. I allowed the Brownian motion to start up again, and the ice boiled. Egor shrieked and dropped his cup.

'Sorry!' I jumped up and grabbed the cloth from the sink, then squatted down to wipe up the puddle on the lino.

'Magic's nothing but trouble,' said the boy. 'That was a good cup.'

'Just a moment.'

My shadow raced towards me, I entered the Twilight and looked at the broken pieces. They still remembered the whole, and it hadn't been the cup's destiny to get broken so soon. I raked the shards together with my hand. A few of the smallest pieces that had fallen under the cooker eagerly moved a bit closer.

I emerged from the Twilight and put the white cup on the table.

'Now you only need to pour more tea into it.'

'Fantastic' Apparently this little trick had made a big impression on Egor. 'And can you do that with any kind of thing?'

'Almost any kind.'

'Anton . . . what if something was broken a week ago?'

I couldn't help smiling.

'No, sorry, then it's too late. The Twilight gives you a chance, but you have to take it quickly, very quickly.'

Egor's face darkened. I wondered what it was he'd broken a week ago.

'Now do you believe me?'

'Is that magic?'

'Yes. The most primitive kind. It takes almost no effort to learn.'

I probably shouldn't have said that. The boy's eyes lit up. He was already figuring out his prospects. His profit.

Light and Dark . . .

'But an experienced magician, he can do other stuff too?'

'Even I can.'

'And control people?'

'Yes,' I said. 'Yes, we can do that.'

'And do you? How come terrorists take hostages? You could creep up in the Twilight without being seen and shoot them. Or make them shoot themselves! How come people die of diseases? Magicians can cure them, you said so yourself.'

'That would be Good,' I said.

'Of course! But you're the magicians of the Light!'

'If we do any deed that is unconditionally good, it gives the Dark Magicians the right to do an evil deed.'

Egor looked at me in amazement. Too much had happened over the last twenty-four hours for him to take it all in. But he was handling it pretty well.

'Unfortunately, Egor, Evil is stronger by its very nature. Evil is destructive. It's much easier for Evil to destroy than it is for Good to create.'

'Then what do you do? This Night Watch of yours. . . Do you fight against the Dark Magicians?'

I mustn't answer. I knew that with a devastating clarity, just as I knew I should never have confided in the boy. I should have put him to sleep and withdrawn deeper into the Twilight. But not tried to explain anything to him, not a single thing.

I wouldn't be able to prove anything to him.

'Do you fight against them?'

'Not exactly,' I said. The truth was worse than a lie, but I had no right to tell a lie. 'We keep an eye on each other.'

'Getting ready to fight?'

I looked at Egor, thinking what a bright kid he was. But still a kid. And if I told him now that the great battle between Good and Evil was approaching, that he could be one of the new Jedi of the Twilight world, then he'd be ours.

Only not for long.

'No, Egor. There aren't very many of us.'

'The Light Others? You mean there are more Dark Ones?'

Now he was all set to leave home, abandon Mum and Dad, put on his shining armour and set out to die for the cause of Good . . .

'There aren't many Others in general. Egor, the battle between Good and Evil has been going on for thousands of years, with the balance shifting all the time. Sometimes Good has won, but if you only knew how many people, who had no idea the Twilight world even existed, were killed in the process. There aren't many Others, but every one of them can get thousands of ordinary people to follow him. Egor, if the battle between Good and Evil breaks out, half the people in the world will be killed. That's why almost fifty years ago a treaty was signed. The Great Treaty between Good and Evil, Dark and Light.'

His eyes now opened really wide.

I sighed and went on:

'It's a short treaty. I'll read it out to you – in the official Russian translation. You already have a right to know.'

I closed my eyes and peered into the darkness. The Twilight swirled into life behind my eyelids. A grey banner unfurled, covered with blazing red letters. The Treaty must not be recited from memory, it may only be read:

We are the Others,
We serve different forces,
But in the Twilight there is no difference between
the absence of Dark and the absence of Light.
Our struggle is capable of destroying the world.
We have concluded a Great Treaty, a truce.
Each side shall live according to its own laws,
Each side shall have its own rights.
We delimit our own rights and our own laws.
We are the Others.
We establish the Night Watch,
So that the forces of Light may monitor the forces of Dark.
We are the Others.
We establish the Day Watch,
So that the forces of Dark may monitor the forces of Light
Time will decide for us.

The boy's eyes grew even bigger and rounder.