'Kevin?' she said.

'Yes?'

'Can you see me?'

'Not really, no.'

'I'm in my pyjamas.'

She heard his laugh ring out around the room. It was hard and scornful, and it hurt.

'Shut up,' she said. 'I didn't have to come here, you know. You don't know what it cost me to get here.'

'What did it cost you?'

But she didn't tell him, because then he would know that it mattered to her not to let him down. Instead she said, as unkindly as she could: 'Is this where you live, then? Is this your house?'

He struck a match and lit a candle and a cigarette from it. 'I don't live anywhere,' he said.

'Don't be stupid,' said Tess. 'Everyone lives somewhere.'

'Who's everyone?' he said.

Tess shivered. In the candlelight she could see the stained mattress in one corner, surrounded by a jumble of newspapers and empty tins and bottles. There was an untidy heap of dark blankets in another corner, but Tess would not have touched them, let alone put one around her shoulders.

'Do you live here?' she asked. 'Seriously?'

'Of course not!' Kevin sounded bitter. 'What do you think I am?'

'Where do you live, then?'

'I already told you that.'

'Then who does live here?'

'No one. Some old tramps use it sometimes, when they can't get into the hostel.'

The cold was beginning to hurt. Kevin didn't seem to be aware of how bad it was. By the flickering light of the candle, she could see him looking from one corner of the room to another with that familiar nervousness. She was suddenly close to tears.

'What are we doing here?' she said. 'I don't understand any of this. How am I supposed to help you?'

Kevin shrugged. 'I'm not even sure myself, yet,' he said, 'but I know it's important. There's a rumour going around. The rats want to bring me somewhere.'

'Rats!'

'Yes. You got something against rats?'

Tess had. A rat was one of the things that she had never been and had no desire to be. But before she could say anything, Kevin went on.

'A rat is about the best thing to be in a city like this. They have the run of the place, you know? They never go hungry.' He smiled at the distaste clearly evident on her face. 'They have a lot of fun, too. More often than not I'm a rat.'

He watched closely for her reaction. Tess tried not to show it. The idea filled her with unease. For although she had spent a lot of her time being all kinds of other creatures, she had never considered herself to be anything other than human. But if Kevin spent most of his time being a rat, then what did that make him? It made sense of the way he behaved when he was human, though; his nervousness, the sense that she had when she was with him of there always being an enemy somewhere close at hand.

'Never been a rat, huh?' he said.

'No.'

'Don't worry. You'll enjoy it. But there's quite a stir going on about this cold weather. At least, I think that's what it's about. Everybody's suffering, you know, not just the people. That's why I came looking for you. They want me to meet somebody. I don't know who it is, but it's a long way.'

As Tess watched him, the tense expression left his face, and there was a momentary confusion in his eyes as he said: 'I didn't want to go there on my own.'

There were suddenly too many questions. There was too much to share with this strange boy, and possibly too much to cope with. And it was too cold to face any of it.

'I have to go home,' said Tess. 'I have to get warm and think it over.'

'But there's no time to think it over. This thing is important, Tess. This weather's getting worse all the time.'

'Do you think I don't know that? Don't you realise I'm getting frostbite standing here?'

Kevin bit his lip. 'I'm sorry,' he said. 'I wasn't thinking.' He began to take off his coat.

'Don't be ridiculous,' said Tess. 'What difference does it make if you freeze instead of me? The point is, the whole thing sounds ridiculous to me. How can we possibly have any effect on the weather, whatever we do?'

'I don't know,' said Kevin, zipping up his parka again, 'but I do know this. Most of my life I've been going in and out of the animal world, and never before did they take any particular notice of me. But now they have. They know that I'm different and they're asking me for something.'

'I'm totally confused, Kevin,' said Tess, 'and I'm too cold to think straight. I have to go home.'

'But we can go straight away,' he said. 'Come on. You won't be cold once we get moving.' As he spoke, he was pointing towards a large hole in the skirting beside the fireplace.

'As a rat?' said Tess.

'Of course.'

Tess shook her head, and at the same moment changed back into an owl. She hopped out of the window and flew straight up and away towards the park. Gradually the activity warmed her and she began to feel better. The whole idea was crazy. All she wanted to do was to curl up in her own bed and forget all about it. But she was not allowed to. As she landed lightly on the edge of her bedroom window, she realised that Kevin was right behind her.

CHAPTER SEVEN.

KEVIN AND TESS STOOD in her room, facing each other.

'Goodnight, Kevin,' said Tess.

'Oh. You're going to bed, are you?'

'Yes.' She wanted to close the window on the night and all that was in it and allow the room to warm up, but she couldn't do that until he was gone. Instead, she climbed into bed and wrapped the covers around her.

Kevin wandered round the room, examining her things. It made Tess uncomfortable. It always made her uncomfortable when someone less well off than she was came to the house. She had no pride in her standard of living, and in situations like this she felt rather guilty.

'You've got a lot of books,' said Kevin.

'Observant, aren't you?'

'Have you read them all?'

'Most of them.'

He took a thick volume out of the book case and opened it. 'You like mythology, then?'

'My dad does. He buys most of that stuff.'

'Do you read it?'

'If I'm bored enough.'

Kevin leafed through the book. 'This is a good one,' he said. 'I haven't seen this one before.'

Tess sighed and tried to drop him a hint by turning her face to the wall, but he went on: 'I spend hours in the library, you know.'

'Oh? When you're not rummaging through people's dustbins?'

She couldn't see him, but she could imagine the look on his face in the brief silence before he said: 'Yes. Or raiding their kitchens or waking up their babies at night. Rats are OK, you know, you shouldn't underestimate them. They have their own codes of behaviour, even if they're not like yours. They have a language, too.'

'All animals do.'

'No, not really. All animals have ways of communicating, but the rats actually have a language, a sort of visual language.'

Tess said nothing, and after a while, Kevin went on: 'I love all this stuff, though, all those heroes and G.o.ds and wonderful beasts. It's the best thing about people, if you ask me. Their imagination.'

'I didn't ask you,' said Tess, and as soon as she had said it, she regretted it. It was just one step too far.

Kevin hurled the book across the room. It hit the wall above her head with a loud crack and landed on the pillow in front of her nose. She sat up in bed.

'For G.o.d's sake, Kevin!' she said, as loud as she dared. 'You'll wake my parents!'

'Your parents? Your precious mammy and daddy? Who cares? Eh? As long as you're all right, all warm and cosy with your feather duvet and your central heating and your own private little life. The rest of the world can go hang, can't it, as long as you're all right, Jack!'

'Shh, Kevin, don't shout! I don't know what you mean, can't you understand that? I don't understand what you're asking me to do.'

'Nor do I!' said Kevin. 'But I know that it's important. And even if it isn't, I have to find out.'

He came over to her and sat on the edge of the bed. Tess's nerves were on edge, waiting for the sound of her father's feet in the hallway.

'You have to help me, Tess,' Kevin went on. 'You just have to. I can't do this on my own. For one thing, I don't have very much time left.'

'What do you mean?'

'It doesn't go on for ever, you know, this thing, this ability we have. Did you know that?'

'No.'

'Only until we're fifteen.'

'How do you know?'

'Someone told me. She was one of us, too, but now she isn't. She learnt it from another Switcher. After her fifteenth birthday she couldn't change any more. That's the end of it.'

The news came as a blow to Tess. She had always believed that her gift would be with her for the rest of her life, the one thing she could be sure of.

'We all meet someone who tells us,' said Kevin, 'and we all meet someone we have to tell. I don't know how it works or why, but it seems that it always does. Anyway, the point is, I'm nearly fifteen, you know? And I'm nervous about what's happening.'

'So you want me to come along and hold your hand?'

Kevin looked crestfallen, and suddenly Tess didn't know why she was putting up such a resistance and being so unkind. She lay back on the pillow to think about it, and Kevin sat quietly, glancing at her from time to time in his nervous, sideways manner.

Tess realised as she lay there that there was nothing to think about. If she refused and sent him away, she would never know what it was about and whether her gift had given her a part to play in some scheme or other. She would have to live with that uncertainty for the rest of her life. No matter how crazy it seemed, she had to go. There was no choice.

She sighed and threw back the covers. A look of delighted surprise crossed Kevin's face. He turned away quickly so that she wouldn't see it, but she could still see the way he felt by the spring in his step as he crossed the room. She pulled on her jeans on top of her pyjamas, and then two sweatshirts, a thick jumper and two pairs of socks. Then Kevin waited in her room as she crept downstairs, feeling like a burglar in her own house, to get her down jacket and gloves.

Back in the bedroom, Tess hesitated. Whatever anxiety she had about the risk she might be running for herself was nothing compared to the feeling that gripped her now. For some reason she knew beyond any doubt that she would not be returning to that room before morning, and that her parents would have to face the shock of coming in and finding it empty. She felt sick, but there was no longer any question of turning back. With hands that trembled more from tension than from cold, she searched through the drawers of her desk for some notepaper that her aunt had given her for Christmas. The she sat down and picked up her pen.

The paper had delicate impressions of swans in blue and gold. Kevin leaned over her shoulder as she wrote. 'Nice paper,' he said.

'Shh.'

'Dear Mummy and Daddy,' she wrote. 'I have to go away for a little while. I'm sorry, but I can't explain to you why. But you must trust me, just this once. Don't send anyone to search for me. It would only be a waste of time. I promise that I will take care of myself, and you must promise me that you will do the same and not worry too much. I will be back as soon as I can. Love you with all my heart, Tess, x.x.xx.x.xXX'

'Yuck,' said Kevin. '"All my heart."'

Tess swung on him. 'Shut up,' she said, in a vicious whisper. 'Shut your filthy mouth. Just because you haven't got anybody.'

He shrugged and turned away, and Tess was sorry, because she realised for the first time that it was true. He had n.o.body. n.o.body at all.

She pinned the note to her pillow and took a last look round the room. Then, side by side with Kevin, she walked to the window.

The two owls swept away again over the city. Kevin led the way back towards Connolly Station, but instead of returning to the flats, he headed for a small patch of wasteland in the same area, where houses had been demolished to make way for some new building project which had never materialised. They overflew it once or twice, checking out the area, and then they began to descend.

There was a crowd of young men gathered around a car a couple of blocks away, but they were not close enough to be a danger. The owls flew a little lower over the wasteground again and, to Tess's horror, her sharp night eyes saw that the whole area was swarming with rats. There was a high chain-link fence around the plot, but nonetheless the local people had managed to turn the place into a dumping ground for their rubbish. Mainly it was large things, old couches with the stuffing hanging out, broken TVs and fridges and mattresses with bulging springs. But there were black plastic bags there as well, spilling out their contents of empty tins and vegetable peelings and tea bags. A perfect breeding ground for rats.

As the owls spiralled cautiously downwards, there was a sudden flurry of rapid movement as the rats leapt for cover, and then there was nothing. Absolute stillness. Into this, the two birds landed, and before Tess could even take a breath, Kevin had dissolved before her eyes and become a rat.

It was strange to watch it happening. If Tess had been asked, she probably would not have been able to describe what it looked like, because it looked, in a sense, just the way it felt. She had the same dizzying sensation of the world losing focus and becoming fluid, as though the observer also were drawn into the process of change and somehow became part of it. She watched as Kevin trotted away a little distance, then stopped and looked back. Tess stood still, with her wings folded, looking around her with large eyes that missed nothing, even in the darkness. The rats were everywhere, poking their noses out of the tin cans and paper bags and carpet folds where they had taken cover. Kevin sat up on his tail and twitched his whiskers with that same nervousness that carried into his human form. Tess wanted to be with him, but she was stuck. She just couldn't bring herself to make that change.