'Haven't you got a match?' she said.

'Good thinking,' said Kevin, fumbling in his pocket.

The first match he struck hurt their eyes so much that they couldn't see the watch. As the second one was burning down, Tess held the watch up close to it.

'The twenty-eighth,' she said.

Just before the flame died, she caught the look of dismay in Kevin's face. Their situation seemed even more hopeless than before, if that was possible. But Kevin said: 'Never mind.'

'Never mind?'

'I was just thinking we might have had a bit of a party, that's all. But we'll have to skip it.'

'A party? Are you out of your mind?'

'No. It's part of the tradition, apparently. The girl who told me about it had one. I didn't really know her very well. She wasn't like you. But she invited me to her party, and I went. The day before her fifteenth birthday.'

'Why the day before?'

Kevin laughed. 'You can't very well throw a party if you're an eagle, can you?'

'An eagle?'

'Yes. She was into discos and motorbikes and stuff. An eagle suited her, actually. It was her kind of thing.'

'You mean ... You mean you can choose?'

'Of course!' said Kevin. 'Didn't you know that? Whatever you are at the time of your birthday, that's what you stay. You can't Switch any more, that's all. But there's nothing to say you have to be human.'

Tess stared into the darkness, trying to take it in.

'I've spent months worrying about it,' Kevin went on. 'Ironic, isn't it? Months trying to choose between a rat and a sparrowhawk and an otter, and now it looks as if I won't have a choice at all when it comes down to it. I'll just have to take whatever I get.'

'No, Kevin,' said Tess. 'We could still get back.'

'How?'

'Somehow. I don't know.'

'I don't see how we could. But in any case, I don't seem to be too worried about it. I can't understand it, really, but ever since Lizzie said what she did, about us having more power than we know, I've had this kind of faith. I'm not worried about those things any more. They don't seem to matter.'

'But you can't just end up as a polar bear or a walrus! You're human, Kevin, you have to be human!'

He laughed again, and Tess felt her heart fill with despair.

'Why?' he said.

But she couldn't tell him. She couldn't explain that she wanted to dress him up and take him into a French restaurant, or that she would welcome him any time she got off the bus and found him waiting. Even if her pride would allow it, it made no sense out here, with the Arctic gales blowing all around them.

'I never was any good at being human,' he said. 'Even with my family, even before I knew what I was.'

'Why not?'

'I don't know. I just didn't have the knack. My brother did. He was older than me, and he got along OK with everyone. My father's a toolmaker, and he does a lot of work at home. Makes all kinds of bits and pieces that people want. My brother was always out in his workshop with him, helping him. But I couldn't take an interest in it. I always got everything wrong, no matter how hard I tried.'

'So what? That doesn't mean anything.'

'It did, though. It meant that I didn't fit in with the men in the family, you see. And my mother ...' He stopped.

'What about your mother?'

'I don't know quite how to explain it. She was always there, always. She never had a job, she never went anywhere, she was there every day when I came home from school and she did all the things that mothers are supposed to do. But in another way she wasn't there at all. She wasn't there for me. Her mind was always on something else, on what she was doing or on what' she was listening to on the radio, or on something that she kept locked away inside herself somewhere.'

Tess noticed that the snow cave wasn't as warm as it had been. The cold seemed to be creeping through her from below, and she turned on to her side to relieve the discomfort in her back.

'When I look at it now,' Kevin went on, 'I see that she just didn't have it, that thing, whatever it is, that attention that people give to each other. I don't blame her for it. But at the time I used to think it was my fault, that I just wasn't good enough to be worth bothering with. But then I got angry about it, and it worked, because at least when I was bad she took some notice of me. That was around the time I discovered I could turn into a rat. It was ages before I discovered that I could be other things as well. In those days I used to set off for school in the mornings and spend the day with the other young rats, and even when my parents knew I was playing truant, there was nothing they could do to stop me. If they left me to the school in the morning, I'd slip off somewhere at break and do a bunk. The other kids hated me because I was different, and I hated them because they weren't.'

'I know the feeling,' said Tess.

'Yes. And as time went by I stopped bothering to go home. When I did turn up from time to time, they used to get into this awful flap and talk about borstals and reform schools, so I thought it was best to just stay out of the way.'

'Did you never spend time being human then, after that?'

'Oh, yes. I still turned up for their birthdays and Christmas, things like that. After a while they just accepted it and stopped asking questions. And I told you I spend ... spent a lot of time in libraries. Sometimes I'd meet someone on the way and hang around with them for a while. But I never had a real friend. Not until ...'

'Until what?'

'Phew. It's getting cold in here, isn't it?'

'Yes. We're not as warm as the bears were. What were you going to say just now?'

'It doesn't matter.'

Tess rested her head on the crook of her elbow. She was colder than she had realised, and beginning to feel drowsy again. She knew that it was dangerous. She remembered reading about it, about how the cold sends you off to sleep, and then you never wake up again. For a while she resisted and pulled herself awake to listen to Kevin's steady breathing in the darkness. What if they both fell asleep here? No one would ever find them. If the weather changed and the ice melted, their bodies would slide into the sea and be lost for ever. The thought of all those fathoms of dark water beneath them filled her with horror, but also a strange sort of resignation. They were so small in the middle of all this. Air, water, ice, and nothing else for hundreds of miles. Suddenly, there was no more resistance. She allowed her mind to drift away wherever it wanted, and there was a deep, deep sense of comfort.

The forgotten scene from the earlier dream returned. It was a landscape as bitter as the one outside their snow hole, but there was something moving across it, some kind of animal. And suddenly, Tess was wide awake.

'Kevin!'

He jumped at the urgency in her voice and she knew that he, too, had been asleep. 'What?'

'I've got it! All that stuff about what isn't.'

'Have you?'

'Yes. It's so simple, I can't believe we didn't think of it before.' She was determined to stay awake now, and she sat herself up so that the top of her head was wedged against the roof. 'Lizzie was right. We're completely caught up in the things around us, just trying to copy what already exists. But what about something that used to exist, and doesn't any more?'

Kevin was holding his breath, and Tess could feel his sense of excitement. 'Go on,' he said.

'Well, what about when there really was an ice age? There were animals that lived in those times, weren't there?'

'What, like dinosaurs?'

'Yes. Except that the dinosaurs didn't make it. They didn't adapt. But some other creatures did.'

Kevin let out his breath with a gasp. 'Mammoths!' he said.

'Exactly! I saw them, Kevin, just now in a sort of dream. Walking through the snow. And why shouldn't we? I'm sure we could. We know what they looked like. I'm positive we could get a feel for them.'

'Of course we could. It'd be a lot easier than a whale.'

There was no more to be said, and they fell silent, their minds full of new hope. After a while, Tess said: 'Kevin?'

'Yes?'

'We ought to be bears again. Until the morning. It's too cold in here. It's dangerous.'

'Yes, you're right,' he said, but he didn't Switch, and Tess had a feeling that he was waiting for something. 'Don't go to sleep again,' she said.

'No. I'm not. I was just thinking.'

'What?'

'Well, if I got stuck as a mammoth. If my birthday came.'

Tess said nothing, thinking about it, and he went on: 'I know there's nothing you could do about it. I wouldn't ask you to stay with me or anything. But maybe you could ... I don't know, just keep an eye on me somehow. So I wouldn't be completely alone.'

'Of course I would, Kevin. I'd do anything. I'd go to the ends of the earth if I had to.'

'I know you would,' he said, and then he laughed. 'You already have, in a way, haven't you?'

Tess's pride reared up. 'I didn't come here just because of you, you know,' she said.

'I know that,' said Kevin. 'But you're still the only friend I ever had.'

Before she could answer, he was a bear again and, with a sigh, she joined him.

CHAPTER EIGHTEEN.

THE TWO MAMMOTHS MOVED slowly but solidly across the snowfields. Their long, woolly coats provided perfect insulation against the blizzards, and their s.h.a.ggy eyebrows and whiskery nostrils protected them from the effects of the freezing air. So little heat escaped through all that insulation that snow landing on their backs didn't melt, and even provided a further layer of protection.

It also provided a partial shield against the sensitive infra-red scanners in the planes that pa.s.sed from time to time above their heads.

'Anything new, Jake?'

'Naa.'

They were flying low this time, through the white heart of the blizzard. There was little or no danger of encountering anything in the air. The high points in the pack ice were well charted, and their radar screens would give warning well in advance of anything that might be in their path, but even so, Scud found it nerve-wracking to be flying so totally blind.

'That freighter out of the way?'

'What freighter?'

'You said there was a freighter.'

'h.e.l.l,' said Jake, 'that was an hour ago. He'll be over Stockholm by now.'

'Nothing else?'

'No. Wait a minute, though.'

'What?'

Even Hadders put down his book for a moment.

'Nothing. Infra-red's just picking up a couple of animals down below. Small ones. I don't know how they can survive down there.'

'Poor suckers,' said Hadders.

'Poor suckers?' said Scud. 'They're poor suckers? What about us?'

The only danger that the mammoths were aware of was hunger. There was no source of food for miles around, not even the rough Arctic vegetation on which they had learned to survive in the past. Their reserves of fat would keep them going for a while, but for how long they didn't know. It took a lot of energy to keep those ma.s.sive bodies warm, and a lot more to keep them moving.

But keep moving they did. Tess and Kevin had pa.s.sed another test. Kevin's faith had held, even if Tess's hadn't, and circ.u.mstances had proved him right. The mammoths were slow but they were comfortable, and they were making steady progress towards the north.

The hours pa.s.sed. The human parts of their minds chafed at the tedium of the changeless landscape, but the mammoths had learnt patience over the generations, and plodded along tirelessly.

The krool sensed them coming long before they were able to see it, and its small, uncomplicated brain went into a momentary seizure. For although it was a poor thinker, its memory was as long and as ancient as its life, and it was well acquainted with mammoths. The prospect of encountering these two was not a pleasant one.

A dead mammoth is an agreeable snack for a krool, but a live one is a different proposition entirely. This particular krool had once had the experience of swallowing a whale which had been trapped beneath the ice, unable to breathe and dying. Its phenomenal internal temperature had crippled the krool, and it had never forgotten the agonizing days that followed as it battled with the heat the way a person battles with infection. Even two live mammoths would not be as bad as that, but they would nevertheless create a considerable disturbance in its system, and it would have to lie up for a while until they were digested.

In the normal course of events, a krool would not even consider eating a mammoth, which was one of the reasons why the mammoths had come to survive their last colonisation of the earth. A krool encountering a mammoth in the usual course of events would flatten the leading edge of its mantle so that the mammoth wouldn't know it was there and would merely continue on its way, traversing the krool's back until, after a few hours, it reached the other side. If this particular krool had not been so hungry, it would have left the two mammoths to go along their way. But it could not allow any source of food to escape, even if it caused a belly-ache. It lay still and waited.

Some miles away, Scud Morgan's bomber had completed an in-flight refuelling operation and started its return journey. In a few more hours it would make a radio-controlled landing on the salted runway of an air base in central England and its crew would get out of their air-bound prison.

Jake was dozing. Hadders was reading. Scud was flying as low as he dared, for the sake of producing adrenalin.

Tess and Kevin blundered straight into the waiting krool. One moment there was nothing ahead of them except untrodden snow and the next, a whole section of it lifted and towered above them, and they were gazing with horror at the black underbelly of the krool. For an instant, Tess thought that the world had collapsed and she was staring into nothingness, a gaping abyss. Then she saw the eye. A single, huge, unblinking eye, gelid and green, looking straight at her.

If Lizzie had been wrong, it would have been the end, not only of the two mammoths, but of Tess and Kevin as well. For the mantle was above them now and the huge, cavernous maw was opening as the krool pushed forward to swallow its prey. But if Lizzie had been wrong she would not have sent the two young Switchers out to test their strength against the krools. Lizzie knew, and quicker than thought, Tess knew too, that they did indeed have powers beyond their wildest dreams. Kevin had been right. If they hadn't been faced with the ultimate test of their skills, they might never have learned them. Because, if there had been time for thought, Tess would never have believed that what happened next was possible. The krool's mantle was dropping like a monstrous fly swatter. Not even a bird would have had the speed to dodge out from under it. But Tess Switched, quicker than she had ever Switched before, and suddenly the krool was rearing away again and backing off.