'No.' Tiaan found tears in her own eyes. 'I can't be your mother, can I?'

'I had a mother, but the nylatl killed her.'

Silence.

'What would you like me to be, Haani? An aunt; a friend?'

'I had aunts. The nylatl killed them too. And ...' She looked up at Tiaan. 'You're too old to be my friend.'

'How old do you think I am?'

Haani studied her. 'Really old. At least fifty.'

'Fifty? You little wretch! You need a good beating for even thinking such a wicked thing.'

Haani stepped well back, though she did not look alarmed. 'How old are you?'

'I'm twenty, as it happens. I'll be twenty-one very soon.'

'When is your birthday?'

Tiaan calculated. It had been two and a half weeks away when they left Itsipitsi, eleven days ago. 'It's not tomorrow, or the day after, or the three days after that, but the day after that. It's in six days' time.'

'Twenty-one.' Haani seemed to be weighing up the numbers.

'I could be your older sister.'

Haani considered that. 'I've always wanted a big sister.'

'Well, that's settled. I'll be your big sister.'

Tiaan gave her a sisterly hug; after a moment Haani pulled back, saying, 'I'm hungry.'

'So am I. Let's have our dinner. I don't suppose you found any water?'

'Way down there!' She pointed, then held out her hand. 'Come on! I'll show you.'

Tiaan took the hand. They ran and skipped across the chamber, where a room had implements recognisable as taps. Haani wound an S-shaped lever and water gushed from a spigot. She tried the other with the same result. Tiaan filled her pot. They sat on the floor, eating cheese, onion and very dry deer meat.

'I wish we had something different, for a change,' Tiaan said. 'We'll have to see if any food was left behind.' She was worried. They had enough for a week and a half, or two if they really stretched it, but what then? It was a long week's trek to Itsipitsi, and nothing to buy food with when they got there. If this place had been abandoned for years, perhaps centuries, there was probably nothing edible here either.

'I can look while you're doing your work,' the child said.

'All right, as long as you don't go too far. And don't do anything dangerous.'

'Of course I won't.'

They slept in one of the few rooms with a window, so they'd know when it was morning. That seemed to matter, somehow. At first light they breakfasted, went exploring but failed to find any food. On the way back, Haani put her head in through a doorway and said, 'What's this place?'

'A bathroom, I'd say. Want to try it?'

'What is a bathroom?' Haani asked.

Tiaan explained. It was a curious one, for when Haani wound the taps water sprayed out of the walls and ceiling. 'I think you're meant to stand under the water and wash yourself,' Tiaan said.

The water was not unpleasantly cold; better than they were used to. Haani was about to get out when she said 'Hey!' and put her hands out against the spray.

'What's the matter?'

'It's ... getting hot.'

Tiaan eventually got the flow adjusted so that it was just perfect. What a luxury! Not even the breeding factory had hot water coming out of a tap. It was the ultimate mark of civilisation as far as Tiaan was concerned, far more impressive than the architecture outside, or the extraordinary machines.

The following day Haani was busy on some project that she carefully kept secret. A birthday present, Tiaan guessed. She went back to the room with the three sentinels and began dismantling the machines. She could recall each of the images Minis had shown her, and how she was to put everything together. Remembering was the easy part.

She made a start. Without proper tools, it was abominably difficult. By the end of the day she had not taken apart the first machine. At this rate it would take weeks. Minis would be dead by then, and so would they; of starvation.

She sat down, wiping her brow, for the room was warmer than the rest of Tirthrax. Haani came running in. 'Look what I found!'

She had in her arms a good-sized ham off some unidentified animal, completely encased in black wax. Tiaan's mouth watered.

'Better let me try it first. It might be no good after all this time.'

'Of course it will be good,' said Haani.

'Well, maybe not, if it's five hundred years old ...' Tiaan peeled back the wax with her knife and carved a strip of meat off. Almost as hard as wood, it was the colour of coal, with a hot, spicy flavour. She tried a small piece. It was delicious, though it burned the tip of the tongue. She had some more. She was used to hot spices, and so was Haani.

They sat companionably, eating the meat and cooling their mouths with draughts of water. 'If only I had some tools,' said Tiaan. 'This work is so slow.'

'What kind of tools?'

'All sorts. Like those in my little toolkit, only bigger.'

'I found a whole room full of tools the other day,' said Haani.

'Why didn't you say so?'

'I didn't know you wanted them.'

With more tools at her disposal than she had names for, the work proceeded swiftly. Bored with her own company, Haani wanted to be part of the great project. The child proved to be surprisingly useful, fetching, carrying and steadying parts while Tiaan assembled them, or just being company, sometimes silent, sometimes chattering.

Tiaan now found that she missed Haani when she was out of the room. The child filled a void that had been there ever since Tiaan had left home. Haani had become family. A real family, like other people had. Soon Minis would complete it.

Her eyes rested on the child, who sat on the bench humming and swinging her legs as she screwed a tapered topaz crystal onto a threaded silver tube. Tiaan smiled. The child did feel like her little sister. Looking up, Haani caught her eye and smiled back. It warmed Tiaan from top to toe. They both deserved a little happiness. And Minis And Minis.

Within days the zyxibule was complete. Tiaan walked around the contraption. She could think of no words to describe it adequately. It was quite as bizarre as its name suggested. No, not bizarre it had no symmetry at all, though when she stood back Tiaan could see a certain alien beauty in it. It rested on five slender legs made from a soft, lustrous rock that had the look of soapstone but the colour and translucency of amber. Each leg was carved in intricate, swirling patterns.

On the legs rested a thick plate, flat in the middle but dished at the perimeter, with a seven-lobed rim. It was made of no substance Tiaan had ever worked with before. It had the lustre of metal a deep blue-black. It was light, hard and strong, but when she tapped it, it rang as if it was made of porcelain. An intensely blue glass, swirled with patterns that repeated at every scale, was fused to the underside.

She had constructed the zyxibule on top of that plate. It was framed by four doughnuts of clear glass, the largest two spans across, the smallest about half that. Wires ran through their walls here and there, terminating inside in little pieces of shiny foil. The doughnuts were arranged largest on the bottom, lying horizontally, up to smallest at the top, nearly two spans above. Each was set about with magnets so strong that when once Tiaan touched a spanner to one, she and Haani together could not pull it off. Tiaan had to set up a block and tackle to do so, and succeeded only after the most gruelling effort.

The third doughnut was fixed vertically, sitting inside the top and bottom ones and enclosing the smallest, which lay horizontally in the centre, not touching. Within that was another glass structure that Tiaan found difficult to describe, or even look at. It was a tube rolled and twisted back to join up with itself, but its inside seemed to become its outside then inside again. Tiaan could not see how it was made. Her eye found it hard to follow the curve of the thing, and kept sliding off it. Twisticon, Haani called it.

Within, around and above these structures was attached a profusion of wires, tightly wound metal coils, clusters of tubes and rods, mysterious constructions of wire and a host of the incomprehensible mechanisms she had spent so long studying on the third day. Everything was connected to everything else but nothing seemed to do do anything. anything.

'I'm sure that's it,' Tiaan said, stepping back. She had spent all day going through the test procedures. Each part worked as she had been told to expect. She had tried to contact Minis several times but there had been no response. She felt a chill of terror every time she thought about that.

'What is it for?' asked Haani, gnawing at a piece of green cheese.

'It is to bring my lover to me,' said Tiaan. 'Ah, but I'm tired. We'll begin in the morning.'

FIFTY-EIGHT.

'Where the hell are we?' cried Nish, staring into the impenetrable darkness.

S'lound let out a mirthless chuckle. 'Not the sea, anyway. A bog, by the smell of it. And not a very deep one either.'

So it proved, when a cold day dawned some hours later. They had gone through thin ice into a waist-deep pond. There were reedy bogs all around, but little wind at ground level, so the balloon had stayed upright once the weight went off it. S'lound climbed up to the brazier, reporting nothing but mire in every direction. Ullii took one look at the place and retreated to her basket. Nish fed the skeet with a couple of half-frozen rats from a bin. The messenger bird screamed and tried to take his fingers instead.

'Now what?' said Nish as they ate bread and cheese for breakfast, washed down with swamp water.

'Gather reeds for fuel,' said S'lound. Nothing seemed to upset him. No doubt he'd had many worse days as a common soldier.

Nish picked a handful of reeds. 'No heat in these. We'll never get off the ground.'

'Soak 'em in tar spirits. That'll get us high enough that we can look for some wood.'

Nish doubted it. The expedition was turning into another disaster and this one was entirely his responsibility. Of course, they might not be able to walk out of this place at all. They might die here.

They spent the day gathering reeds. It was tedious work in the freezing water and sucking mud, and after labouring for about nine hours, all the daylight they had, the pile of fuel was depressingly small. Late in the afternoon Ullii came out of her basket and collected a bundle of reeds, handing it to Nish with the air of someone bestowing a great gift. It was, had Nish only realised it, but he was in no mood. He snapped at the seeker, who retreated to her basket, deeply hurt, and did not come out all night.

It was too late to take off that afternoon. The following morning, Nish's prediction proved correct the damp, hollow reeds generated hardly any heat at all. The ones soaked in spirits of tar were better, exploding as soon as they were tossed in the brazier. The first time it happened Nish fell off the ladder into the water and emerged covered in smelly mud. Had it happened in the air, he would have been killed.

'Less spirits,' said the imperturbable S'lound, lifting him over the side all black and dripping.

It was nearly midday by the time they were ready to go but the balloon did not budge. The basket was stuck in the mud. They had to rock it free before it would lift, and then sluggishly. Once in the air they caught a breeze and drifted west over swamp, lake and yet more swamp. There was not a stick of wood to be seen.

S'lound leaned on the edge, cheerful as ever. Nish scrunched himself up in the corner next to Ullii's basket, pulled the coat over his head to keep the drifting flakes off, and felt a failure in every respect.

He was disturbed by a cold nose pushing against his cheek, an arm going over his shoulder. To his amazement it was Ullii.

'You are sad, Nish,' she said softly.

'We'll never get out of here. We'll never find her. I've failed again.'

She sat quietly beside him. Nish was touched. She cared about him.

'I can see trees!' called S'lound.

Nish jumped up. A scrubby patch of forest had appeared out of the foggy distance, and just as well. The reed bundles were exhausted.

It was almost dark when they landed by the forest. The following morning they chopped wood for several hours, and had a good bit stacked in the basket, when Ullii cried out.

'What's the matter?' yelled Nish.

'Someone coming.'

A tall man was advancing towards them, waving a wooden spear and shouting in an unknown dialect. There was a host of angry villagers behind him.

'Any idea what he's saying?' asked Nish.

'We're stealing his wood.'

'There's wood everywhere. It's rotting on the ground.'

'Nonetheless, it's his.' S'lound sprang up on the side and began shouting back, waving a menacing broadsword. 'Get the fire stoked up,' he said over his shoulder.

'We're ready to lift.'

'Untie the ropes.'

Nish climbed out. The balloon was already putting pressure on the knots. He got them undone but the balloon went up too fast. Afraid of being left behind, he gave a triple turn of the rope around his wrist. It tightened and jerked him up. A spear whizzed between his legs, close to parts he was particularly fond of.

Ullii gave a shrill scream. The rope felt as if it was going to tear right through his skin. If it came undone he was dead. They were already as high as the treetops.

He snatched and caught the rope with his left hand. It eased the strain a little. Then S'lound was leaning right out, hauling him up and grabbing his free hand to make sure he did not fall. Nish was pulled over the side and dumped on the floor. Ullii herself helped to bring him down, and when he lay there, gasping, she kissed him on the nose, an astonishing intimacy.

'I can see the sea,' S'lound said as the sun was setting.

Nish scrambled to his feet. 'We'd better put down. We can't afford to go over the water.'

'Then what?'

'We gather fuel and wait for a southerly to take us north to the mountains.'

'Shouldn't be too long a wait,' said S'lound. 'Feels like it's blowing from the South Pole right now.'

He was still saying that a week later. This time they'd gone to see the villagers and made an arrangement with them for fuel. Nish was canny enough to pay in coppers, which they were glad to have, and the villagers chopped and fetched a mountain of wood, enough to enable them to keep the brazier going the whole time. If the air in the balloon went cold it would take hours to fill it.

The wind blew from the west, the north and even the east, but never from the south. Nish fretted. What was Tiaan up to? Ullii had sensed great urgency the last time she'd seen seen her. They had, however, found out where they were, somewhere between the cities of Runcil and Tatusti. Ullii had managed a clear sighting on Tiaan. Assuming she had not moved, the intersection showed her to be near Mount Tirthrax. her. They had, however, found out where they were, somewhere between the cities of Runcil and Tatusti. Ullii had managed a clear sighting on Tiaan. Assuming she had not moved, the intersection showed her to be near Mount Tirthrax.

Late on their eighth night in that place they were woken by a great buffet on the basket. The wind whistled through the ropes, a gale carrying not snow but stinging crystals of ice. It was a howling southerly that lifted the balloon with every blast.