Everyone outside the cage was down, apart from Loc Ifrahim and Avernus and Yuli. The surviving drone dropped down in front of the three of them as they stood with their wrists cuffed, looking all around them, and a man stepped out of the entrance to the garage and airlocks and told them to remain absolutely still.

'I'm a diplomat,' Loc Ifrahim said. 'A non-combatant taken prisoner and held here illegally.'

'I know who you are,' the man said. He was bareheaded in a pale grey pressure suit scuffed with black dust. His face was pale and expressionless. His eyes were masked with a pair of spex.

Loc Ifrahim said, 'If you know who I am, then you know that I'm on your side.'

'You are not the only reason why I am here,' the man said. He moved about the fallen Ghosts, picking up their weapons and throwing them one after the other in high tumbling arcs onto the roof of the blockhouse. He stooped over Sada and picked up her pulse rifle and walked to the perimeter of the cage and studied the prisoners, his gaze moving from person to person, settling on the woman who had started the chant.

'Zi Lei,' he said. 'I've come to save you.'

4.

The spy entered the research facility through the airlock beside the garage. He cycled through into a locker room where a small army of bright orange pressure suits hung along two walls, shucked his helmet, and put on his spex and sorted through his zoo of demons. One forced the local net to handshake with his spex and two more slipped through and began to peel back the layers of security that protected the facility's AI.

Within ninety seconds, the spy had access to every camera in the surveillance system in the dome and the blockhouse. He saw people lying dead or unconscious in offices inside the blockhouse: clearly there had been some kind of serious quarrel or mutiny. He saw Avernus and her daughter and the diplomat Loc Ifrahim standing in the compound outside the blockhouse, handcuffed with five other prisoners and guarded by men and women in white suit-liners and white pressure suits. He saw prisoners inside a razor-wire enclosure, all of them sitting on the ground except for one. It was Macy Minnot, talking to a young woman in a white pressure suit who stood on the other side of the wire. He couldn't see Zi Lei, and inspected the seated prisoners one by one and there she was.

A strong wave of pleasure moved through him. For a moment, studying Zi Lei as she sat cross-legged in orange coveralls, her dear familiar face, he forgot about his mission. He even forgot about his injured shoulder. It was hurting badly now, but he wouldn't let the suit treat it with painkiller because he needed the clarity that painkiller might dull.

Then one of the demons handed him control of the two drones that floated in the air, monitoring the prisoners inside the wire. After that, it was simply a matter of selecting targets and letting the drones do the rest.

It took less than a minute to knock down everyone outside the razor-wire enclosure except for the diplomat and the gene wizard and her daughter. The spy should have called for a retrieval crew then, and made sure that his targets were secure until pickup. He didn't. He wanted to free Zi Lei first. He wanted to make sure that she was safe. He wanted to make sure that she could reach a place of safety before the retrieval team arrived.

So he stepped out into the compound and got rid of the weapons dropped by the people who'd been knocked down by tranquilliser darts, and called to Zi Lei. They stood with only the razor-wire between them and he told her how glad he was to have found her safe and sound, and started to explain that he would free her and let her take one of the rolligons. But instead of bubbling over with gratitude and relief, as he had imagined she would, she was furious and close to tears, and the other people in the enclosure, clearly mistaking him for someone fighting on the side of the city, were all shouting at him, demanding to be freed.

He told them to be quiet and when they didn't obey he jacked the stock of the pulse rifle against his hip and blasted a chunk of the mesh floor of the enclosure. In the ringing and shocked silence he told Zi Lei that he had done everything for the best of reasons. Staring straight at her as he tried to project his candour and concern, and also keeping watch, through the link with the surviving drone, on the three handcuffed prisoners behind him.

'I asked you for help,' Zi Lei said. 'I trusted you, and you gave me up to the peace officers. Why should I trust you now?'

'You don't have to trust me. You don't have to believe anything I tell you, except for one thing. I came here to help you.'

The spy would have said more, but the prisoners were growing mutinous again. Some called out to him; others, including Macy Minnot, had begun to pry at the gate with lengths of pipe. Trying to lever it off its hinges. He fired another shot into the floor and told them all to stand back. This wasn't like any of the simulations and scenarios he had practised. There was no script. He wasn't acting this out but living inside it, excited and hopeful and exasperated and upset. Zi Lei was upset too, begging him not to hurt anyone.

'The war has begun and you have to get away from this place,' he told her. 'There are two rolligons in the garage. Take one of them. Drive out of the crater and keep driving. Find a shelter or an oasis and wait there. I'll find you when this is all over. I promise.'

'What about my friends?'

'This is about you and me, Zi. They'll have to take their chances.'

'Free them, Ken. Free all of us. This is why we were brought together. Don't you see? They are working through you right now, but you're resisting it. I know you're a good man. Let them do good, through you.'

He realised that she was talking about her fantasy of the Edda, and it broke his heart.

'I have one more thing to do. Just one more thing, I swear. And then we can be together, and I can explain everything.'

'I won't leave without my friends,' Zi Lei said, and turned from him and floated away from the razor-wire.

The spy called after her and told her that they would leave together, and when she didn't reply he brought the drone across the compound to the wire. He couldn't think of any other way of dealing with the prisoners. He had to neutralise them before he opened the gate and freed Zi Lei and made Macy Minnot his prisoner; otherwise they'd probably try to rush him, and then he'd have to try to kill some of them or all of them. And even if he could do it he didn't think he could bear it, afterwards. He would explain it to Zi Lei later. He would explain everything.

He saw the two of them climbing into one of the rolligons, driving out of Romulus Crater across a rolling plain, past craters and ranges of wrinkle ridges to one of the oases scattered everywhere. They'd wait out the war there. Just the two of them. He would take the people he'd been ordered to locate to a shelter and secure them and send a message to the retrieval crew, and then he would drive off with Zi Lei. He knew it was a fantasy but he didn't care. He wanted it to be true and that was all that mattered.

'What I have to do - it's for us,' he said.

A moment later, the drone began to take down its targets.

5.

Walt Hodder clutched at the dart that sprouted on his chest and his eyes rolled up and he collapsed beside Macy. Everywhere in the cage men and women were falling where they stood or running and falling headlong. Outside the razor-wire the drone rose higher, turning this way and that with tiny precise flicks, targeting people trying to hide under tables or behind those who had already fallen.

Zi Lei was shouting at the young man who stood masked and resolute, begging him to stop hurting her friends. And on the other side of the compound, Yuli bounded over to the woman sprawled unconscious in her pressure suit and jerked out the dart lodged in her chest-plate and ran straight at the man. He staggered when she leaped onto his back, dropped the pulse rifle and clawed at her. But she had already danced away, poised on the balls of her feet with a dancer's grace, watching calmly as he pulled out the dart she'd stabbed into his neck. He took two wavering steps towards her and fell to his knees, groping vaguely for the pulse rifle. She snatched it up and slammed its stock against the side of his head, and he toppled over and lay still.

The drone was slanting along the razor-wire fence, taking down the last of the prisoners. Yuli flipped the pulse rifle end for end and fired from the hip. The drone jolted sideways in the air, one wing sheared away, and spun to the ground. Her second shot kicked smoking pieces of the machine across the compound; her third shattered the casing of the gate's lock.

As Yuli and Macy dragged the gate open, Zi Lei ran out and knelt by the man and cradled his head in her lap. His spex lay askew on his face and a thread of blood crept from one nostril and edged across his cheek, shockingly bright against his pale skin. He didn't look at all menacing now; simply young and helpless, a callow knight who'd failed his first serious test. Zi Lei bent to listen to his stertorous breathing, her black hair falling around his face like a wing, and looked up when Macy asked who he was.

'Ken. Ken Shintaro. From Rainbow Bridge, Callisto. He's on a wanderjahr.'

'You know him from the city?' Yuli said.

Zi Lei nodded. 'He must have come here to save me. He wanted to make things right after he let the wardens arrest me.'

'I doubt that very much,' Yuli said flatly. She was holding the pulse rifle in both hands, pointing it off to one side of where Zi Lei knelt with the unconscious young man. Telling Macy and Avernus, 'It's plain that he's either a traitor, or an infiltrator working for the Brazilians. He didn't come here to make anything right. He wanted to capture us, for exactly the same reason that the Ghosts wanted to take us away. We're valuable assets. Spoils of war. That's why we weren't shot full of tranquilliser like everyone else.'

'A higher power was working through him, but he didn't realise it,' Zi Lei said. 'He had to give me to the wardens so that I would be brought here. And when I was brought here he came to rescue me, and saved everyone else.'

'I believe I had something to do with that,' Yuli said. 'And I'll deal with him, too, if it comes to it.'

'Remember who you are,' Avernus said sharply. 'We are not like those who consider themselves our enemies. We will not hurt or kill anyone.'

'I could take care of him,' Zi Lei said.

'I don't think so,' Yuli said. 'It's too dangerous to take him with us, and it's too dangerous for you to stay.'

Avernus said to Zi Lei, 'You trusted him, and he betrayed that trust. Think very carefully, my dear. Can you trust him now? Truly?'

Zi Lei looked down at the unconscious young man she was cradling. After a long moment she looked up again. Her eyes were starry with tears but her face was set as she shook her head left and right.

'We'll lock him up here, with the Ghosts,' Avernus said. 'He'll be quite safe. And no doubt his friends will find him, sooner or later.'

'If he doesn't get free first, and cause more trouble,' Yuli said.

'What about Loc Ifrahim?' Macy said.

'The diplomat? I suppose the Brazilians wanted to rescue him,' Yuli said.

'I mean, where is he?'

Yuli looked all around, then sprinted across the compound. Macy chased after her, through the locker room to the inner door of the airlock.

It had been jammed shut. Through the port, they could see Loc Ifrahim fastening himself into an orange pressure suit. Yuli banged on the port with the stock of the pulse rifle; he lowered the helmet over his head, grabbed Sada's ceramic knife from the floor - he must have used it to cut his plasticuffs - and hit the release switch for the outer door and was veiled in a brief mist as it swung open. He turned and mockingly waved bye-bye and stepped through, and the door swung shut on his heels.

By the time Macy and Yuli had found pressure suits that more or less fitted them and pulled them on and gone out through the garage, there was no sign of him. They climbed a walkway that curved up the side of the research station's dome and looked all around but failed to spot the fugitive. Beyond the dark patchwork of vacuum-organism fields, the long, low ridge of the crater's rim swept across the horizon. The upper part of the city, angled against the rim's shallow slope, shone like a splinter of glass. Tiny lights flared and faded around it.

'One thing I know,' Yuli said over the short-range band, 'you can't stay here a minute longer. Neither can my mother.'

'First we need to make sure everyone is safe.'

'Let me do that. I'll make sure everyone gets away from here. Even the guards and the Ghosts. But it will take time for them to shake off the effects of the tranquilliser. And there is no time. You must leave right now, and take my mother to a place of safety. I assume you know somewhere suitable - you've lived here long enough.'

'I can think of one or two places,' Macy said.

'Find a good place to hide,' Yuli said. 'Then we can work out how to get my mother off this moon. Which she should never have visited in the first place. It's time to regroup and rethink.'

'What about you?'

'You think I'm a little girl,' Yuli said. 'I'm not. It would be better to think of me as a monster. Let's go inside. It isn't going to be easy, persuading my mother to see sense. I'm going to need all the help I can get.'

6.

Arvam Peixoto wanted to oversee the endgame of the battle of Paris from the ground, and insisted that Sri Hong-Owen accompany him. He allowed her to bring Yamil Cho, his one concession, and they flew down from orbit in a transport that carried technicians, marines, and a brace of battle drones in its belly. It came in fast and low, skimming above the plain south of the conjoined rims of Remus and Romulus Craters, then pitching up and climbing past long fans of fallen rubble and terraced cliffs and setting down near a small pressure dome that had taken a bad hit - the spars of its framework were twisted and warped and broken, the few surviving panes frosted white.

The transport's belly door dropped open and the technicians and marines rolled out in three armoured personnel carriers and sped away along the rimtop highway. The city's surviving fusion plant had been secured and the technicians were going to check out its control systems, reaction chambers, heat exchangers, and transformers, and search for booby traps and any attempts at sabotage. Sri and Yamil Cho rode with Arvam Peixoto in a fourth APC to the transport hub at the top of the city's tent, with the two battle drones pacing ahead and behind.

Arvam explained that the perimeter defences had been rolled back and pretty thoroughly stomped on, but there were still pockets of resistance inside the city, and a fair number of snipers who were taking shots at any invader who strayed into their cross-hairs. He was animated and exuberant, pointing out a shallow crater where some small engagement had taken place, breaking off to talk to his aide, listening to something on his phone, then telling Sri that it wouldn't be long now. The marines had fought their way into the railway station at the top of the city and the freight yards at the bottom - it was just a matter of advancing both fronts towards the centre and then mopping up.

'We're trying to open a line of communication with the mayor so that we can ask him to surrender,' Arvam said. 'We've already been contacted by two different officials who want to sue for peace, but as far as we can tell they aren't plugged into the command structure. We don't even know if there is a command structure; it's possible that not even the mayor can stop the fighting.'

He took a call on his phone and then studied his aide's slate, telling the woman to organise defensive positions around the compound and make sure that the park on either side of the river was thoroughly searched and surveilled, turning back to Sri.

'The fighting was bad outside, and it will be twice as bad inside. This is their city. They have hiding places, spiderholes, they know how to move from place to place without being spotted . . . But don't worry about any of that. I have some good news. Avernus's compound has been secured. So cheer up, Professor Doctor. You're on the winning side. You've put yourself on the front line of history. Because history is definitely being made today. When Paris falls, the other cities will fall too. It's a brutal lesson, but necessary. And with any luck you'll get all you want, and more.'

'You have Avernus's compound, but you don't have Avernus.'

'Not yet.'

'We don't even know if she is still on Dione. If she's alive or dead.'

'Wherever she is now, alive or dead, you get first look at her last home. And pretty soon you'll have access to all the places where she worked her magic. If she is dead, figuring out all her secrets should keep you busy for the rest of your life,' the general said, and turned away to take another call.

Sri was having a hard time hiding her growing misgivings. As far as she was concerned, everything hinged on finding Avernus alive, but the battle for Paris was now in its final stages and there was no sign of the gene wizard, no clue as to where she'd been taken after she and her daughter and crew had been arrested by Marisa Bassi. And there was no sign of the spy who had infiltrated Paris weeks before, either. He'd planted a bug in Avernus's compound and had mailed hours of recordings just before Paris's net had fallen over, but so far he hadn't made himself known to the invading force. Meanwhile, Sri was at Arvam's mercy, his to use as he saw fit, his to discard when he decided that she was no longer useful. And Berry, still sleeping in his hibernation coffin, was his too. A hostage Sri had willingly given up as a guarantee of her cooperation. At least Alder was safe. The thought of her brave, capable son alive and well in the sanctuary of her fortress of solitude, protecting and continuing her life's work, was her only comfort.

The APC ground through a gap cut in a slumped ridge, and the city was revealed. Its long tent, ridged and faceted, ran down the inside slope of the crater rim to the crater floor, bending like an elbow at its midpoint and stretching away amongst a jumble of small domes and blockhouses. Swirling layers of smoke pressed against the tent's huge panes down its entire length, obscuring the buildings and parks inside. Paris was burning. Sri felt a stab of excitement and apprehension. Avernus was somewhere down there. In the city, or out on the plain of the crater's floor. Must be. Had to be.

The APC drove down a ramp into a big airlock whose outer doors had been wrenched away. The inner chamber was marked by scorch marks and gouged by shrapnel and small-arms fire. Most of the lights had been shot out. Everyone in the APC sealed their pressure suits and disembarked, moving carefully in the slight, dreamlike gravity, and cycled through a small auxiliary airlock and emerged in a covered plaza. The battle drones stooped through the airlock one after the other, and then the party set off down a stalled escalator encased in a glass tube that slanted to one side of a horseshoe-shaped waterfall, the source of the river that ran down the centre of the city.

The pumps that drove the river's recirculation had either been damaged or switched off. The waterfall was dry, and so was the river bed that ran away downhill between meadows and stands of trees where small fires smouldered. A squad of pressure-suited marines was guarding the beginning of a road that meandered off through the trees. Arvam Peixoto unlatched his helmet and tossed it to his aide, shook hands with every one of the marines and took their lieutenant off to one side and talked to him for a few minutes before clapping him on the shoulder and walking back to Sri and the others.

'We're clear to go all the way to the bottom,' the general said. 'You can all unlatch your helmets, by the way. The air's perfectly breathable.'

The marines had rounded up half a dozen two-seater trikes with fat, low-gravity tyres and composite frames painted bright primary colours. Sri rode pillion behind Yamil Cho, following Arvam Peixoto and his aide down the steep white road. The two battle drones loped alongside, their cowled bodies swivelling this way and that. Trees strung with platforms and nets and cableways flowed past, sprawling stands of flowering bushes, glimpses of meadows. Tiers of smoke hung at different levels under the framework that supported the faceted ridges of the tent's roof, drifted around banks of lights suspended from the roof. There was a strong odour of char and burnt plastic. Something was on fire amongst trees close to the road - a wrecked battle drone collapsed amongst uprooted trees, burning with a fierce heat that Sri felt against her exposed face as they sped past. She thought of the entire forest catching fire; the entire city. She mentioned this to Yamil Cho, and he told her that no one would have time to put out fires. 'They are either fighting or hiding from the fighting.'

The road forked and they turned left, rumbling over a bridge that humped above the river. Two bodies in civilian clothes were tumbled against each other in the dry river bed below the bridge's span. Blood dyed a long pool of water caught amongst rocks. On the other side of the river, a white flat-roofed building was on fire. Dense black smoke tumbled from a big hole knocked in its walls and thinner streams of smoke issued from every one of its windows. Bodies were scattered across a broad plaza.

They cut away from the road, following a short track between stands of puffball pines that fell away to reveal a one-storey building with blind white walls. Sri's heart gave a little kick. She recognised it from surveillance photographs: the compound where Avernus and her crew had lived until they had been arrested.

It looked untouched. A smart-wire barrier had been strung across its square entrance and at one corner several marines in armoured pressure suits stood or crouched, watching the city burn.

Everyone climbed off the trikes and Arvam Peixoto took Sri by the arm and steered her past the marines, followed by his aide and Yamil Cho and two battle drones. One of the marines told him that the area was still unsecured, but the general shrugged off the warning and gestured grandly towards the city and told Sri that if Avernus was hiding there she would soon be found.

Beyond a big park of trees and grass crossed by white paths, the centre of the city was framed by the arch where the sloping section of the tent met the section that lay more or less flat on the crater floor. Open-plan low-gravity helices and honeycombs of public buildings and apartment clusters, cased by the transparent organic shapes of secondary tents, stood amongst parks and plazas on either side of the broad dry river bed, with the gridded blocks of the older part of the city stretched away behind them. Threads of smoke rose everywhere, feeding a thickening haze. Sharp snaps and banshee whoops and rattling fusillades came from near and far. Arvam pointed to several places where the fighting was fiercest and explained that the citizens of Paris had set up barricades at intervals down the main avenues and at the bridges across the river. Every building was defended and groups of fighters were using service tunnels to move about under the city.

'My men have to risk their lives to clear each block, and after they move on the sons of bitches pop up behind them and start firing. They started most of those fires, too,' Arvam said. 'It looks like they'd rather destroy their city than surrender it, which is why we need to end this as soon as possible.'

There was a falling whistle truncated by a flat bang as something struck amongst the trees behind the compound. Then a sprawl of white roses at the edge of the park in front of the compound vanished in a fountain of red flame and black smoke. Smouldering pellets of dirt floated down all around Arvam laughed. 'Mortars! They're using mortars on us!'

The battle drones rose up, weapons pods everting their sheaths, as a third explosion blasted everyone with stinging dirt. Yamil Cho pulled Sri down; the aide crouched; Arvam drew his pistol and loosed off shots in the general direction of the park. A moment later both drones started firing, fire flashing from the fretted barrels of their recoilless guns, the noise tremendous as streams of explosive slugs laced with red tracers hosed out across the park and converged on a building at the far edge. A wall disintegrated; the flat roof collapsed. A small figure scooted out and was caught by intersecting lines of gunfire and torn apart and flung aside.

The drones ceased fire at the same moment. Standing still as statues with smoke drifting from the muzzles of their guns. Arvam Peixoto broke the ringing silence, his voice sounding flat and shrill as he shouted at the marines who were guarding the compound, ordering them to get down there on the double and clear out the buildings along the perimeter. They jogged past, spreading out in a line, and another mortar whistled down. The explosion tossed one of them into the air and he tumbled limply and lay still. The drones started firing again, taking out the front wall of the building next to the one they'd already demolished, stopping in unison.

Two marines knelt over their fallen comrade. One looked at Arvam and shook his head and the general told him to leave the man there.

'Freeze him and leave him. You've got a war to win.'

The marines pulled out a body bag, rolled the dead man into it, and sealed it up and pulled the tag to start the chemical reaction that would lower the temperature inside to 2 Centigrade.