'The fact that we are having this conversation proves that you can't hide.'

'You forget that I invited you here.'

Sri was pleased by this small shot of defiance. It meant that Avernus was human after all, with human weaknesses - pride, vanity, fear - that could be exploited.

'The war is over,' she said. 'Your side lost. My side won. You can't pretend that you can escape the consequences of that, any more than the Outers can pretend that they have nothing to do with the rest of humanity.'

'Herring gulls,' Avernus said.

After a moment's furious thought, Sri said, 'I'm not sure what you mean.'

'A species of seabird once common on both sides of the Atlantic. I believe they became extinct during the Overturn.'

'Ah. I myself have done a little remediation work in the Antarctic. I revived two species of albatross and five species of penguin. Also skuas. I suppose someone working in the northern hemisphere might have revived these gulls. I can easily check.'

'Herring gulls exemplified a problem in classical taxonomy, before genome analysis became commonplace. In those days, you may recall, members of a species were considered to form a reproductively isolated breeding group whose genes did not combine with those of outsiders. There were various subspecies of herring gull ranged around the eastern and western shores of the Atlantic. A continuum in a geographical circle broken at one end,' Avernus said, lifting her staff and using its silver-shod end to sketch a half-circle in the air. 'Each subspecies was able to interbreed with its neighbour. But the two subspecies from either end of the geographical range were unable to interbreed - they were infertile with each other.'

'I must suppose that your history lesson has a point,' Sri said, irritated by the way that the gene wizard used this very small gap in her knowledge to steer the conversation in an unexpected direction.

'Your people believe that the Outers are becoming estranged. Another species. Entirely separate from the baseline species on Earth. They don't see that there's a continuum,' Avernus said, sketching the half-circle again. 'Nor for that matter do the extremists amongst the Outers. Each end of the continuum would destroy the other, but if you destroy the part of humanity furthest from you, that makes the part next to it the extremity. Which must also be destroyed. And so it goes, removing segment after segment from the continuum until there is only one segment left. And that will turn on itself.'

'You think I think that? Well, I don't,' Sri said. 'I don't believe in the old ideas of species and separatism. In reducing life to the level of the survival and reproduction of single genes. No, I believe in the unbounded potency and adaptability of life. I believe in exploring its every potential expression. I know you believe that too. These creations of yours are proof of it.'

Sri's breath was raw in her throat, her heart beat was loud in her ears, and she felt as if she was standing naked before Avernus's pitiless scrutiny. But she felt euphoric, too. She had thrown off her caution and laid bare the conviction at her core and set it at Avernus's feet like a challenge. Whether the old gene wizard chose to accept or reject it, whether she chose to cooperate or whether she would have to be coerced into cooperating, Sri's declaration of her credo would be the cornerstone of their collaboration.

For a long moment there was no sound but the bubbling hiss of steam from vents and the skirl of wind over ice-rock. Then Avernus said, 'You made me an offer, Professor Doctor Hong-Owen. Let me make a counter-offer. Come with me. Work with me.'

'Why would I want to do that?' Sri said.

'Because I know that the kind of work that you want to do will soon no longer be welcome on Earth. The political climate has changed. Moderates who permitted the use of genetic engineering to help regenerate the planet's damaged ecosystems are losing ground to the radical greens. And the radical greens believe that genetic engineering is a hubristic interference with natural law. That it once helped feed billions of people during the hard years of climate change and the Overturn is of no consequence to them. They believe that it is as damaging to what they call Gaia as the petrochemical addiction that fuelled global warming. Already they are destroying genetically engineered crops. They are planning to shut down research programmes, including your own. And they have come out here to take control of our cities and habitats because they fear what we might be capable of, what we might become.

'You have no future on Earth, Professor Doctor, or anywhere that lies under Earth's hegemony. But I can take you to places beyond Earth's reach. If you come with me, I can show you many wonderful things, and give you the tools to create wonders of your own.'

Before Sri could answer, a sharp and distant crack like thunder rolled across the sky.

'Enough talk,' Yamil Cho said. 'Don't you know what that was?'

'You will be quiet,' Sri said, angry and astounded at his temerity.

'She's been spinning you a line and you're so infatuated that you don't see it,' Yamil Cho said. 'Drawing this out while her trap closes on us. As it has. That was a sonic boom. Something is approaching; from its radar signature it looks like an aeroshell.'

'My offer is genuine,' Avernus said. 'You have already left your old life behind, Professor Doctor Hong-Owen. All you have to do now is take a last step, and come with me.'

'Enough,' Yamil Cho said again. He had drawn his pistol and pointed it steadily at Avernus as he walked towards her along the crest of the ridge.

'You will stop this right now,' Sri told him.

'I will not. I am no longer your servant. And Avernus is not your prize.'

'Whose, then?'

But Sri already knew; knew now why she had been allowed to chase after Avernus.

'General Peixoto believes you don't have the best interests of the family at heart. And from what I've heard here, he's right,' Yamil Cho said, and turned back to Avernus. 'You will come with me. You can walk, or I'll cripple you by shooting you in the legs, vent your air supply until you lose consciousness, and carry you out of here. That's my offer.'

Sri raised her pistol and squeezed the trigger, but nothing happened. Yamil Cho laughed, asked her if she really thought he would have trusted her with a working weapon. And with sudden hot black fury Sri shouted at him in a rising cadence: 'Unfeasible forfeit! Drop dead! Drop dead! Drop dead!'

He dropped dead. Clutched at his head, buckled at the knees, fell flat on his face.

Sri ran. She took three bounding leaps and vaulted the narrow sleeve of the pool and came down on a low terrace of the ridge with a shock that shot clean through her, from the soles of her feet to the crown of her skull. For a moment, the weight of her lifepack threatened to topple her backward into the pool. But she clung to the gnarly ice-rock, her gloved fingers and the toes of her boots jammed deep into crevices, pulled herself up to the top of the ridge, and grabbed the pistol from Yamil Cho's outflung hand and straightened up and aimed it at Avernus.

Who stood leaning on her staff some twenty metres away, a small black indomitable figure, face pale and calm behind the faceplate of her helmet. 'I suppose that I must be impressed,' she said.

'A simple fail-safe,' Sri said.

She'd inserted it when she'd cut Yamil Cho to sharpen his reflexes and give him control of his sleep patterns. Not because she didn't trust him any less than the rest of her other servants, but because she didn't trust any of them: those closest to her and her sons had all been equipped with fail-safes or cut-outs. Yamil Cho's was a simple parasitic circuit in his inner ear that responded only to her voice and controlled shunts in his internal carotid arteries. Triggered by the code words, it had blown the walls of the arteries and caused a massive cerebral haemorrhage.

Avernus said, 'Did you murder your creature as a sign of your good intentions?'

'He betrayed me. I won't ever countenance that.'

Sri was back in control of herself again, except that she couldn't quell a faint tremor in the hand that held the pistol.

'My offer still stands,' Avernus said. 'Will you come with me? We can be on our way before that aeroshell arrives.'

'You're wrong about Earth. Things have changed for the moment, but they will soon realise that they need me. Need us.'

'You are a scientist. Don't let yourself be blinded by pride.'

'I would have preferred that you entered into our partnership voluntarily, but there it is. You will come with me, and we will work together, as equals,' Sri said, and felt an intense relief wash through her when Avernus began to walk towards her, slow and cumbersome in her black pressure suit, leaning on her staff with every other step.

'What about your creature's body?' the old gene wizard said.

'Let him rot here,' Sri said carelessly.

'It's a desecration of my garden. Also a waste of useful biomass. He can feed my ice worms.'

'Ice worms?'

'In the pool,' Avernus said, and gestured with her staff.

Sri glanced down and saw stout black tendrils rising stiffly from smooth-lipped crevices at the bottom of the pool. 'No,' she said, suspecting some kind of trick. 'We'll leave him where he lies. And get rid of the silly staff, too.'

Behind the faceplate of her helmet Avernus's smile was overlaid by the reflections of red and green pinlight indicators. She straightened her arms in a crucifix pose and opened her hand and let the staff drop past the steep flank of the ridge into the pool below.

Sri knew immediately that she'd made a mistake. But before she could move or even cry out the staff plunged straight into the gelid water, creating barely a ripple as it sank down and caught amongst the black tendrils at the bottom, and the tendrils exploded in a mass of threads that shot up with amazing speed, erupting from the pool in an explosive burst of vapour that shot up higher than the top of the ridge and froze in an instant snowstorm that swirled about Sri and Avernus and fell away. Tangles of black wire filled the pool from edge to edge and shot out over the rim in every direction, dividing as they extended and dividing again, rising and spreading and scrambling like a time-lapse video of a growing briar patch. A mass of wires overshot the edge of the ridge and whipped around on either side of Sri in a prickly embrace. She stepped back with jittery haste, lost her footing and fell flat on her back. Before she could bounce up she was caught in a thickening cocoon that wrapped around her arms and legs and torso, tightening as she kicked and struggled.

'I would advise you to stay as still as possible,' Avernus said.

The old gene wizard stood at the centre of a tangled cloud of black thread. None of it quite touched her; when she stepped forward she pushed aside masses of finely divided wire like someone opening a curtain and left behind in the frozen cloud a hollow in the shape of her pressure suit, which Sri realised must be coated with some kind of inhibitor.

'The feeding tentacles of my ice worms contain capsules homologous to the desmoneme nematocysts of coelenterates like jellyfish and sea anemones,' Avernus said, looking down at Sri. 'As in coelenterates, they discharge tangling threads when stimulated. The threads are a species of thermotrophic smart wire, very like that used in mines designed to incapacitate rather than kill. They stretch towards anything that has a higher temperature than its surroundings, and divide and cling tight to it. As they cling tight to you. If you move too much, Professor Doctor, the tentacles of the ice worms will sense it, and they will contract and drag you into the pool.'

'The staff,' Sri said, stupid with astonishment and fear. She was still holding the pistol, but her hand and wrist were bound tightly against the thigh of her pressure suit.

'Its hollow tip contained a saturated solution of potassium chloride and proline to stimulate mass firing. And just before you arrived, I added a little something to the pool to bring the worms to the surface. Usually they live deep in the vents. Big slow creatures, up to five metres long. They can subsist for years on ammonium and hydrogen fixed by symbiotic bacteria, but to grow and reproduce they need organic matter. I never did get around to designing the rest of the biome I planned for the vents, so they have to be fed every so often. Usually we cut down a few of the parasol trees,'

Avernus said. 'But a human body will do just as well.'

She stooped over Yamil Cho and with surprising deftness unlatched his helmet and pulled it away. Frost instantly bloomed on his face. The old gene wizard unlatched his lifepack, too, then straightened up and with the toe of one boot began to rock his body to and fro. It slewed sideways as the threads that tangled around it jerkily contracted, turned on its side as it was dragged over a spur of ice-rock, and suddenly vanished over the edge of the ridge.

Sri heard the splash when it struck the pool. Although her helmet was caught fast in a web of threads she could turn her head inside it, and saw fog boil up around the edge of the ridge and blow away as snow. 'What will you do with me?' she said.

'The threads will disintegrate in a few hours. As long as you keep still until they do, you won't be harmed,' Avernus said, and stepped past her, picking her way through rigid tangles of black wire, moving out of sight.

'If you free me now,' Sri said, 'I'll forget all about this. We can work together as equals.'

'I would advise you to study my gardens very carefully before you talk to me again,' Avernus said.

'This isn't the end of it,' Sri said. 'You know I won't stop looking for you, and I plan to live for a very long time.'

Avernus did not reply.

After a minute, Sri was struck by a horrible vision of being marooned here and said loudly, 'If you take my ship, it'll make it even easier to find you.'

No reply. Sri switched from channel to channel, but there was only silence on the radio, and the faint scratch of wire on ice-rock all around her, and the mournful fluting of the wind.

She lay still, pinned to the top of the ridge like a sacrifice in some arcane ceremony. Feeling a seeping chill in her shoulder blades and buttocks and heels, looking up at the frozen curds and canyons of the sullen cloudscape that sheeted the sky from horizon to horizon, trying not to think about what would happen to her if Avernus had lied about the ice worms. But there had been no reason for the gene wizard to lie, she told herself. She would be free soon enough. She had enough air for a day, plenty of water. She would live through this.

Soon enough, the aeroshell glided low overhead like a UFO from the paranoid dreams of the long ago. Sri wondered if she was going to be taken prisoner or hostage, wondered how she could explain this to Arvam Peixoto. It would be easy enough to work up a story that fixed the blame on Yamil Cho, she thought, and vowed that whatever happened she would make good her threat: she would spend the rest of her life searching for Avernus.

13.

Newt feathered the aeroshell close to the shuttle that sat at the centre of the elevated platform and brought it down on the cushion of its fanjets and kept it in trembling balance, ready to scoot off in an instant, while he and Macy looked all around for any sign of life. The shuttle was buttoned up and cold and the slope of raw black ice-rock that reared beyond it was empty and still. At last Newt cut the fanjets to a whisper and let the aeroshell settle on its landing gear.

Macy levered up from her acceleration couch and squeezed Newt's shoulder and told him that she'd take it from here. 'Stay ready to fly out of here if there's even a hint of trouble.'

'You bet.' He smiled at her through the faceplate of his helmet. They were both zipped into pressure suits because the aeroshell lacked an airlock. 'Don't take long. And take care in this godawful pull. If you break a leg, I'm not sure I could carry you back.'

Titan's gravity was just 0.14 g, but it was much stronger than Dione's. Although gene therapy, drugs, and medichines had spared Macy from the worst effects of low-gravity bone-and muscle-wasting, she hadn't been able to exercise properly in jail, and felt sluggish and cumbersome as she popped the hatch and clambered backward down the flank of the aeroshell and dropped jarringly to the ground. Clutching the pulse rifle to the chest-plate of her pressure suit, she walked the length of the shuttle, studied the path that curved around the flank of the cone towards the little lighted dome, then crept to the very edge of the landing field's cantilevered platform and for a moment forgot her fear of ambush as she stared out with breathless wonder and wild surmise at this new world.

Below her, a steep slope thickly overgrown with filmy carbon-black domes raised on slim stalks, rippling and doffing in graceful waves in the same wind that fluted past her helmet, dropped to a flat floor of black ice several kilometres across, marked here and there by cuneiform featherings of white snow that trailed from vents, and circled round by the caldera's rim. The lower slopes of the rim were grown over with swathes of the same black parasols, and its naked, scalloped crest rose against a sky sheeted with orange smog.

Newt asked her if she could see any sign of Avernus or anyone from the shuttle.

'Not yet. Maybe I should check out that dome.'

'Do the shuttle first,' Newt said. 'After that, everything's gravy.'

Macy's suit told her that someone else wanted to talk on one of the line-of-sight channels. It was Avernus, saying, 'I hope you aren't thinking of stealing that ship. They'll chase you down if you do.'

'We're here to rescue you,' Newt said.

'I'm sure that's part of the reason why you risked your ship and your lives to follow me. But I do not need rescuing and you should not have come here.'

Macy asked Avernus where she was, and the gene wizard told her to look along the eastern rim. 'Just above the tree line.'

There was a long flat ledge under an overhang of dark ice-rock. When Macy zoomed in on it she saw Avernus in her black pressure suit working at one end, slowly and methodically pulling a silvery drop-cloth from a small biplane perched on a slanting catapult mechanism. Macy relayed the view to Newt, who told Avernus that she had to come back to the landing platform right now, that they had to leave as soon as possible. 'The Brazilians have sent another ship after us.'

Newt had spotted the dropship heading out of Saturn towards Titan while he'd been dickering with his friends in Tank Town for use of the aeroshell, something that had cost all his and Macy's present kudos and a share of any they might earn in the next five years.

'Actually, I think I'll stay here for a while,' Avernus said. The old gene wizard was breathing heavily as she worked, but she sounded completely calm.

'Where are the people from the shuttle?' Newt said.

'Look to the centre of the caldera.'

After a minute or so, Macy spotted a figure in a blue pressure suit on top of a long ridge of ice-rock, lying bound and supine amongst what looked like clouds of wire or threads spun from a seething pool at the base of the ridge.

'Professor Doctor Sri Hong-Owen,' Avernus said with a trace of remote other-worldly amusement.

'Is she alone?' Newt said.

'Is she alive?' Macy said.

'She had what I suppose was a bodyguard, but he is gone. And she was still alive when I left her.' Avernus explained about the ice worms and how she had stimulated their feeding reflex when Sri Hong-Own had confronted her. 'I would advise you to set aside any notion of rescuing or capturing her for the moment. Unless you have a supply of 3-hydroxyanthranilic acid. It is the only thing which will prevent the threads latching onto your suits.'

'I think we're all out,' Newt said.

'We can't just leave her there,' Macy said.

'The threads will lose their grip, by and by. As long as she does not struggle she will be fine,' Avernus said.

'I guess you planned this all along,' Newt said.

'Not at all. The opportunity arose by a fortunate confluence of circumstances. You should be careful what you say to each other, by the way. Stick to short-range or line-of-sight channels. Even then, you should assume that she might be listening in. Who knows what Brazilian military technology is capable of?'

Macy asked the gene wizard what she was planning to do. 'If you can't tell me exactly, maybe you can at least give me a hint about what I should tell Yuli.'

There was a short silence. Wind played around Macy's pressure suit as she stood like a disentablatured caryatid at the edge of the landing platform, looking out across the gulf of air to the distant caldera rim where Avernus was folding back the last part of the drop sheet from the tail of the little red biplane.