'Walk calmly,' he went on. 'Don't attract attention.'

Easy to say, but she didn't know if he was helping or kidnapping her. Trust Malien, she told herself. Tiaan did her best to act normally, though it must have been obvious, had the passing Aachim glanced at her, that she was under a strain. Fortunately they took no more notice of her than at any other time.

They'd trudged the corridors and were halfway across the ice pavement outside when someone called out, 'Bilfis, can you spare me a moment?'

'Keep going, Tiaan,' Bilfis said softly. 'Get into the thapter and make it ready for flight. Don't get out no matter what happens, or what I say.' He turned. 'Harjax? I'm just checking some of the maps I left in the thapter.'

'Would you bring the old human back for interrogation, please?'

'Certainly. Tiaan,' he called, 'fetch the maps from the thapter, if you would.'

Tiaan risked a glance over her shoulder as she climbed the side. Harjax stood uncertainly outside the cubular doors, a victim of indecision and Aachim politeness. Tiaan slipped in, put the maps into their racks, carefully inserted the amplimet and made all ready. She felt ill. She'd only flown this thapter a couple of times, and then briefly. Its controls, different from those of her original thapter, could be temperamental. She prayed for a steady hand and a strong stomach.

'Would you fetch her please, Bilfis,' called Harjax, trying to be commanding without alerting his quarry. 'It's rather important.'

'Of course,' said Bilfis, 'if it's so urgent.' He strolled towards the thapter, a picture of unconcern. As he climbed the side he said quietly to Tiaan, 'Ready?'

'Yes.'

'Go, as fast as you possibly can. Fly around the side, then back to the east-facing door. Malien will be waiting there.' He jumped in.

The thapter sprang to life. Tiaan mentally worked the controls, praying she had them right.

Harjax, belatedly realising that something was wrong, began to run across the paving.

'Come on!' Bilfis snapped.

She jerked and twisted the yoke at the same time. The thapter lifted sharply, spinning on its axis, front down, so quickly that she couldn't see where she was going. Harjax sprang out of the way, shouted to the guards outside the doors but again hesitated, unwilling to fire on his own.

Tiaan turned the yoke back, a fraction too far, for the thapter now tumbled end for end while it was still spinning. At least it was slowly gaining height, though it was heading straight for the cubular doors.

'Do something!' Bilfis shouted.

She jerked the yoke, intuition guiding her hand, the machine straightened out and Tiaan took it up vertically. Harjax roared orders to fire but Tiaan sideslipped, hurtled towards the high north-western corner of Stassor, skimmed the flank of its peak and shot over the top, out of sight.

'Down, low to the roof!' hissed Bilfis. 'Weave about, just in case. They've weapons here that could shatter this machine like ice on an anvil, once they find the resolve to use them.'

Tiaan raced across the roof, dropped so sharply on the other side that Bilfis's feet lifted off the floor, corkscrewed around the north-eastern peak out of sight, then zipped back towards the eastern door. There was no one outside.

A shrill piping sounded within, a call to arms, and she saw a squad of soldiers racing down the hall. 'What do we do, Bilfis?'

Just as Tiaan was thinking that Malien wasn't coming, three people threw themselves through the doors. Tiaan slammed into a pancaking hover just to the right of the doors, so the guards could not shoot from inside the hall. The three Aachim flung themselves in and she shot up, piling them all onto the floor.

'Get over that far mountain, quick!' cried Malien, pointing to a range to their east. 'Fly like you've never flown before, or they'll melt us down to tallow.'

Crossbow bolts slammed into the sides. Tiaan spun down the ridge, across the glacier-filled valley and up the other side towards a saddle between two rocky horns. As they were halfway up she felt the field draw down so hard that the thapter missed a beat. The patterns on the glass went wild and she could feel the amplimet flaring in sympathy.

'Over the saddle!' roared Malien. 'Get down into shelter, before it's too late.'

It was still a long way ahead, up a precipitous slope. Tiaan looked back. A tower at the top of the building had developed glowing crimson rings. The whole of the glassy cube of Stassor had gone black. A chill went up her spine. She hurled the thapter hard left, left again, right, up, then down and to the left once more.

The saddle approached, as sharp as a blade. She made for the middle of it, the lowest point. The rings were whirling up and down the tower, faster and faster. She could see them reflected on the glass of the binnacle.

Tiaan was almost to the saddle before she realised that it made the perfectly framed shot the Aachim were waiting for.

'Go left!' Malien's voice was a choked scream.

Tiaan was about to but, as her hand moved the yoke, an urgent sense of wrongness told her that the Aachim were expecting that. She flung the yoke hard the other way, veering right and shaving ice off the rising ridge crest with the base of the thapter.

The low point, as well as the left-hand side of the saddle, exploded in a spray of steam and molten rock, then they were over and hurtling down the sharp decline with an avalanche on their heels.

'Pull up,' said Malien, 'but keep well below the saddle. They might reflect the beam off the ice, even if they can't see us.'

Tiaan was already doing so. The Aachim picked themselves up from the floor, looking at each other. They were unharmed, apart from Bilfis, who had a fleck of blood on the back of his robes, below the right shoulder blade.

He rubbed it, examining his fingertip. 'Just a flying shard.'

'Where to?' asked Tiaan.

'We can't go to Tirthrax' said Malien. 'Not for long, anyway.'

'Or to any of our other known refuges.' said Bilfis, 'since they'll look there in their thaptersMalien considered. 'We've got little food or drink, and only the clothes we're wearing. Head south and west, Tiaan, for the moment.'

'What happened back there?'

'Harjax was uncomfortable with the story of your escape,' said Malien. 'As soon as their first thapter was free, he sent it to the Foshorn, to Vithis. We had a feeling the news would be bad, so we were ready to flee. The urgency of the envoy's return was alarm enough.'

And when he ordered the guards to fire on us,' added Bilfis, 'it confirmed the worst.'

Tiaan looked from one to the other. 'What news did he bear?'

'In your escape, you did more damage than you'd thought. Vithis suffered a broken arm and jaw, and three noble Aachim were killed in the construct that exploded underwater. But there was worse . . .'

'Minis!' Tiaan said, white-faced. 'I killed Minis.'

'You did worse than that, as far as Vithis is concerned.'

'How can anything be worse than death?'

'Oh, for some Aachim, there can be far worse,' Malien said grimly.

Part Five: Air-Dreadnought.

Fifty-three.

'Death in life,' Malien explained sombrely. 'You maimed him, Tiaan. He lost a leg, three fingers, and his pelvis was crushed. He may never walk again; he'll never be without pain. But worse still, he's no longer whole, and every Aachim knows it. To their eyes Minis is a ruined man. If Vithis lives another thousand years he'll neither forgive nor forget. He's declared clan-vengeance against you and all who aid you in any way. Any Aachim who does so faces exile or death.'

'Even your people?' Tiaan whispered.

'Harjax's envoy bound us as well. Perhaps he felt it was a way of allying our sundered kind. Or perhaps he felt as aggrieved as Vithis. I didn't wait to find out.'

And yet you three helped me, at the cost of your own lives.'

'It wasn't just for you,' said Malien. 'There's a higher danger and we can't do without you.'

'The nodes?' said Tiaan.

'The nodes. Bilfis has made a model of the ones near Stassor - those you've mapped - and they're more unstable than he'd imagined.'

'To put it at its bluntest,' said Bilfis, who was a pallid grey, and sweating despite the cold, 'I'm so terrified that I was prepared to break the code of clan-vengeance and become an outlaw. There is a higher duty, when the very world may be at stake.' Nodding formally to Tiaan, he went below.

The remaining Aachim seemed to be assessing her worth. The lean man was Talis the Mapmaker, whom Tiaan had met several times. The stocky one was called Forgre but she knew nothing about him. Without acknowledging her, he followed Belfis and Talis below. A mutter of voices drifted up, in which she heard her own name several times, though she made out nothing more.

Tiaan looked up at Malien, who was staring at her. What was Malien thinking? Was she regretting giving up everything to save her, Tiaan? And poor, maimed Minis, condemned to a living death. Other tragedies, other disasters, though arising out of Tiaan's actions, had ultimately been caused by others. She had done this terrible wrong by herself, out of terror for her life. No, call it by its true name: cowardice. She had maimed the man who, for all his failings, had loved her. He'd been going to help her, she felt sure of that now, and in return she'd hurt him grievously and run away.

'Clan Elienor were blamed for allowing you to escape,' said Malien, 'and have suffered the greatest penalty Vithis could impose. They've been cast out, exiled and their constructs forfeited.'

Guilt overwhelmed Tiaan. The control yoke slipped in her hand and the construct dipped sharply.

'I think you'd better let me take over. Go below and lie down.' Within seconds Malien had ejected the amplimet and taken the yoke. Grim-faced, she flew between the unclimbable peaks.

The day faded. Tiaan lay dozing on her bunk. Malien flew on, torn half a dozen ways. Exile could not hurt her as it did her companions, for among her own people she'd been an outsider since the Forbidding was broken. Even so, to actively defy the entirety of her kind was no small thing. And now Tiaan's life had been laid in her hands - a precious, vital life if the nodes were fading, as Bilfis suspected. What was she to do about that?

Not to mention Clan Elienor. Though the clans had disappeared on Santhenar thousands of years ago, every Aachim knew their heritage. Malien's was the House of Elienor and she was a descendant of the great heroine. Now Clan Elienor were lost somewhere in Taltid. Their homes and means of travel had been confiscated and they had been abandoned to starve in a land stripped bare and plundered by lyrinx as well as human scavengers. Her duty was clear. She must do what she could for her people.

Malien knew roughly where Clan Elienor had to be. They had been left on the coast north-west of Snizort, where they could survive for a time by fishing and collecting seaweed, though when the fish migrated south to the Karama Malama in the winter their position would be dire. There was only one thing to be done. Around midnight, Malien turned south.

Tiaan woke wrapped in blankets but still cold. The thapter was whining furiously, and someone was coughing, over and over. She touched a globe to brightness. It was Bilfis, dabbing at his lips with a cloth that was stained red.

Seeing her staring, he said hoarsely, 'It's nothing. I suffer from mountain sickness. We're much higher than Stassor, here.'

She went up the ladder. It was mid-morning and Malien stood at the yoke, as she had all night.

'We're going back to Tirthrax,' said Malien.

'But you said we wouldn't be safe there.'

'Not for long, anyway,' Malien said tersely. 'We'll fill the thapter with provisions and other essential items, then head west.'

Tiaan, full of guilt and feeling that she was only here under sufferance, asked no questions.

'I plan to share my exile with Clan Elienor,' Malien went on. 'And ask them about the node problem, though they may not be able to help. The nodes of Santhenar must be very different from those of Aachan. It's lucky I have Bilfis. He's the most brilliant of all our field mancers and if anyone can solve this problem, he can.'

Tiaan took turns with her, winding through the passes night and day, and they reached Tirthrax on the third evening after fleeing Stassor. Malien flew inside and the Aachim got out. Bilfis, still coughing blood despite the lower altitude, came last.

'Stay here,' said Malien to Tiaan. 'Keep watch and make sure it's ready to go at a moment's notice. Forgre, would you set a sentinel at the entrance? I doubt if Harjax's thapters could reach here before this time tomorrow, since he has no relief pilots and they must stop to sleep, but we'd better be sure.'

They were gone many hours, during which Tiaan had ample time to reflect on her own problems, though not to find any resolution. The Aachim reappeared after midnight, wheeling trolleys filled with food and wine, bags and boxes of tools and equipment, a number of volumes of the Histories, plus atlases and charts of the western lands. It took until dawn to pack it all inside.

The sky was clear when they departed, and there was no sign of pursuit. Malien ordered Tiaan to set a course southwest, in the general direction of Snizort, and went below.

After an hour in which she got no sleep at all, Malien came back up. They were now flying over the north-western corner of Mirrilladell, a land of a million lakes and bogs. It looked pretty from the air but was scarcely inhabited, being bitterly cold in the long winter, and a mosquito-ridden hell in the short summer. Folktales told that the insects could bite through metal.

'Would you set down, Tiaan?' she said politely. 'Bilfis is no better. Even this height is troubling him.'

Tiaan settled the craft on a bare island in a braided stream milky with glacier-ground rock. They helped Bilfis out. He could not stop coughing.

'I begin to wonder if it can be mountain sickness,' said Malien. She unfastened his coat. 'Hold! What's that?'

There was a fresh stain on the back of his shirt. Bilfis raised a limp hand. 'It's nothing. A chip of stone hit me during the escape.'

'But that was days ago - let me see.' She tore off his shirt. Just below the shoulder blade a little green blister bulged out, leaking pale fluid.

'It's a flac!' said Malien in a rigidly controlled voice. 'Talis, my healer's bag, quickly!' 'What's a flac?' said Tiaan. Malien did not answer.

'A tiny, burrowing dart,' Bilfis said weakly. 'It releases a slow poison into the blood that affects the breathing. It has to be cut out at once.'

And never to be used against our own kind,' said Forgre grimly.

'It was intended for you, Tiaan,' said Bilfis, 'but you swerved unpredictably and I obviously took it instead. An irony, some might think.'

Talis raced up with the bag. Malien selected various bladed tools as well as a long thin pair of tweezers.

'It's too late,' Bilfis said. 'It'll be part-dissolved by now, Malien.'

I have to try. Hold still.'

She began to cut into him. 'There, I see it; she said after some time. 'Tweezers, Talis.'

He passed them across. 'This is a big risk, Bilfis,' said Malien. 'It's very fragile. I don't think I can get it out whole.' 'If it stays in, I die. If you break it, I die more quickly. It's designed so. I'm ready, either way.'

'It never occurred to me that they would use a flac against us,' said Malien, shaking her head.

'It's a forbidden weapon, even in clan-vengeance,' Forgre explained.

'But not against me,' said Tiaan.

'Not against the lesser species.' Malien wiped sweaty hands. Her lips moved in an exhortation, or a prayer. Slipping the tweezers into the slit, she took gentle hold of the end of the flac and tried to ease it out.

They all heard the sound, like rotten metal crunching. Bilfis jerked and his eyes went wide, then Malien was desperately, furiously raking the fragments from the wound and reaming out the residue, heedless of his pain.