. . she can stay down here for a long time.'

Slowly – the space around us resisted sudden movements – I walked over to the wall, parted the branches and looked out.

It was nothing like the human world.

There were glittering clouds drifting across the sky – like steel filings suspended in glycerine. Instead of the sun there was a broad cloud of crimson flame way up high – the only spot of colour in the hazy grey gloom. On all sides, as far as the horizon, there were low, contorted trees, the same ones the witch had used to build her house. But then, were they really trees? There were no leaves, just a fantastic tangle of branches . . .

'Anton, she's gone deeper. She's beyond classification,' Edgar said behind me. I turned and looked at the magician. Dark-grey skin, a bald, elongated skull, sunken eyes . . . But still human eyes. 'How do I look?' Edgar asked and bared his teeth in a smile. I wished he hadn't – his teeth were sharp cones, like a shark's.

'Not great,' I admitted. 'I suppose I don't look any better?'

'It's only an appearance,' Edgar replied casually. 'Are you holding up okay?'

I was. My second immersion in the lower depths of the Twilight was going more smoothly.

'We have to go to the fourth level,' said Edgar. His eyes were human, but with a fanatical gleam.

'Are you beyond classification then?' I asked him. 'Edgar, it's hard for me even to go back!'

'We can combine our powers, watchman!'

'How?' I was perplexed. Both the Dark Ones and the Light Ones have the concept of a 'Circle of Power'. But it's a dangerous thing, and it requires at least three or four Others . . . and anyway, how could we combine Light Power and Dark Power?

'That's my problem!' said Edgar, and began shaking his head about. 'Anton, she'll get away! She'll get away on the fourth level! Trust me!'

'A Dark One?'

'An Inquisitor,' the magician barked. 'I'm an Inquisitor, do you understand? Anton, trust me, I ord . . .' Edgar stopped short and then continued in a different tone: 'I'm asking you, please!'

I don't know what made me do it. The excitement of the hunt? The desire to catch a witch who had destroyed thousands of people's lives? The way the Inquisitor asked?

Or maybe a simple desire to see the fourth level? The most mysterious depths of the Twilight, which even Gesar visited only rarely, and where Svetlana had never been? 'What do I do?' I asked.

Edgar's face lit up. He reached out his hand – the fingers ended in blunt, hooked claws – and said:

'In the name of the Treaty, by the equilibrium that I maintain, I summon the Light and the Dark . . . and request power . . . in the name of the Dark!'

He gazed insistently at me and I also held out my hand, and said:

'In the name of the Light . . .'

In part this was like the swearing of an oath between a Dark One and a Light One. But only in part. No petal of flame sprang up in my hand, no patch of darkness appeared on Edgar's open palm. It all happened on the outside – the grey, blurred world around us suddenly acquired clarity. No colours appeared, we were still in the Twilight. But there were shadows. It was like a TV screen with the colour turned right down, when you suddenly turn up the brightness and contrast.

'Our right has been acknowledged . . .' Edgar whispered, gazing around. His face looked genuinely happy. 'Our right has been acknowledged, Anton!'

'And what if it hadn't been?' I asked cautiously.

'All sorts of things could have happened . . . But our right has been acknowledged, hasn't it? Let's go!'

In the new 'high-contrast' Twilight it was much easier to move around. I raised my shadow as easily as in the ordinary world.

And found myself where only magicians beyond classification have any right to go.

The trees – if they really were trees – had disappeared. All around us the world was as level and flat as the old medieval pancake Earth, supported on the backs of three whales. Featureless terrain, an endless plain of sand . . . I bent down and ran a handful of the sand through my fingers. It was grey, as everything in the Twilight was supposed to be. But there were embryonic colours discernible in its greyness – smoky mother-of-pearl, coloured sparks, golden