'He is angry because he can't win their hearts,' the woman, Zi Lei, said. 'Anger is bad. Like black air.'

He asked Zi Lei what people were trying to do here. He was interested because Marisa Bassi was clearly interested, standing with his arms folded across his chest, watching as the man shouted at the audience and the audience shouted back. After a few moments, the mayor said something to the very tall woman next to him, something that made her tip back her head and laugh loudly.

Zi Lei said something about the communal mind, many of her words lost in the full-blooded baying of the audience. The man in the spotlight threw up his hands and walked off the stage and sat down, and Zi Lei darted forward and leapt to the centre of the stage. Ken Shintaro wondered if he was supposed to follow her. No. He stayed where he was, watching as the jeers and shouts of the crowd died away. A tiny drone floated down, amplifying Zi Lei's voice as she said that there were too many bad vibrations in the theatre and nothing could be done until they were cancelled. Someone started to object but several young men and women near the stage stood up and called for quiet.

Zi Lei stood still in the crossing beams of the spotlights. Her skinny chest rose under her black vest as she took a deep breath and she locked her hands together at her throat and let out a kind of pulsing hum, ohmmmmmm-ohmmmmmm, taking in a breath with each oh, the hum continuous, machine-like, and now members of the audience were humming too, a great engine of sound that continued for more than two minutes before people began to clap. Zi Lei stopped abruptly, bowed, and walked off the stage, passing Ken Shintaro without looking at him.

He followed her outside, curious and excited. He didn't understand what had happened but felt that it was important. Something that he hadn't been briefed about. A discovery of his own. When he caught up with her and asked her what the humming meant, she pulled a folded sheet of paper from a pouch slung on her hip and thrust it at him, crumpling it against his chest. As soon as he took it from her she darted away, crossing the plaza in three bounding leaps and disappearing between the stalls of the green market, gone.

The sheet of paper was densely printed on both sides. There were many exclamation marks. Some words were printed in capital letters or in red or yellow ink. He puzzled his way through it several times. It seemed that wise aliens were watching humanity but were repelled by the disharmony in the universal vibrations that pervaded the Solar System. If these could be tuned correctly, then the aliens, who were called the Edda, would make themselves known. Then they would uplift humanity into a new state of grace.

A search of the net yielded copious amounts of material that Zi Lei had posted about the Edda, as well as a journal detailing her reactions and feelings to the messages she claimed to have received, and comments from people who appeared to treat the whole tiling as a piece of fiction, a work of art. He knew from his extensive briefings that Paris was famous for its artists, storytellers, and theatre, and he supposed that Zi Lei's tracts about the Edda and her journal were part of some kind of elaborate fiction, and that her performance at the Permanent Peace Debate had been something to do with it too - although the way she had briefly united the audience was, as far as he was concerned, strange and frightening. Suppose there was some kind of harmonic that could tune peoples' minds, make them think as one, like the drills of the last days of his training . . .

Ken Shintaro had to work at the farm the next day. There was much to do. Three greenhouses were full of dying crop plants that had to be ripped out and dumped outside in freezing vacuum as a precaution against the spread of disease. Engineers were taking samples from every microalgal monoculture, too; oxygen production was down eight per cent. He overheard two of the engineers discussing the problem. One of them said that it was even worse in Xamba, Rhea, where they'd had to switch over to electrolysis of water to supply oxygen; the other said that on Tethys, both Athens and Spartica had lost their dole-yeast cultures.

His brothers at work, softening targets for the final assault.

When he returned to his room he found another copy of Zi Lei's text folded in half at the foot of the door, weighted by a teardrop of heavy transparent plastic. A message had been written across the crowded print in red block capitals: Are you one of us?

The next day, she came up to him and asked him if he had read her exegesis. It took him a moment to realise that she meant the pamphlet; she was already hurrying on, breathless and choppy as her prose, explaining that she had first met the Edda in dreams, and now she saw their agents here and there.

'I thought at first you might be one of them. I thought you might be a spy.'

For a moment, he felt a jolting convulsion in his chest. It was as if Zi Lei could see right into his skull. See his secret self. Then he realised that she meant the Edda, and calm rolled down from the top of his head and he said, 'I'm a visitor. I was born in Rainbow Bridge and I am on a wanderjahr.'

'I know. I looked you up,' Zi Lei said. She was smiling, showing small teeth white as grains of rice.

They were standing in the park near Avernus's compound. A few people stood in front of the entrance of the square building, brandishing laser pens that branded glowing slogans in the air. Help us in our hour of need. A plague on the houses of Earth. Peace is not the answer. They wanted Avernus to join the war effort and create weapons. Give us guns, not flowers.

Zi Lei asked again if she had read her exegesis; and he said truthfully that he had read it several times but didn't really understand it.

'It's all there, if you read it properly,' Zi Lei said, and added that she had work to do, and walked away.

He didn't see her for two days, and he missed her. Not as much as he missed the familiar company of his brothers, the routine and order of his childhood, but with the same kind of sweet ache, and his heart lifted when he found a mango outside his door and a folded sheet of paper underneath it with a scrawled note. You look tired. This will help.

He saw her that evening, at the Permanent Peace Debate. He sat beside her but she didn't speak to him for a long time, frowning with concentration while three women on the stage discussed a text that hung in the air, taking suggestions from the audience, modifying it. It was some kind of declaration of peaceful intent. At last Zi Lei shuddered all over, said that she had been trying to smooth out the harmonics but it was no good, something was resisting her, and she stood up and walked out.

Ken Shintaro hurried after her, found her sitting on a bench at the far side of the plaza outside. She was very pale, and her hand trembled as she wincingly cupped her forehead. 'It is such hard work,' she said.

'Let me help you,' he said.

He bought her a bowl of noodles. He told her how much he had enjoyed the mango. She didn't say anything for a while, stirring with her chopsticks the noodles coiled in the bath of rich oil-flecked broth. He felt a pleasurable tenderness, watching her. Remembering how he had looked after his brothers when they had fallen ill or had been hurt in the gymnasium, how they had helped him. He urged her to drink some of the broth, smiled when she managed a few mouthfuls and declared that she felt a little better.

'It is such hard work,' Zi Lei said. 'But it is very important. Only I can stop the war, you see.'

He listened patiently to her monologue about resolving tangled harmonies, and the fleet of beautiful ships waiting deep inside Saturn, waiting for humanity to prove itself worthy of joining the great Galactic civilisation.

'I have been shown secret visions in my dreams. I have sworn to use this secret knowledge for the good of all humankind. It is hard, very hard, but I will do it.'

'I have secrets too.'

He just blurted it out. And yet he wasn't horrified or shocked by the violation of his training. Instead, he felt only a kind of giddiness. Happiness, relief.

Zi Lei stood and told him that she had work to do and leaned across the table and kissed him hard on the mouth. They stared at each other with shared astonishment. Then she clapped a hand over her mouth and loped away.

After work the next day, as he was walking towards the apartment building, a woman came up to him and said that she was a friend of Zi Lei.

Ken Shintaro said that he was pleased to meet one of Zi Lei's friends because he hoped that he was a friend of hers too.

'That's what I want to talk about.'

They sat at a tea stall. The woman introduced herself: Keiko Sasaki. She said, 'You haven't been in Paris very long.'

It was a statement of fact that seemed to require no answer. Keiko Sasaki was a slender young woman with a calm, matter-of-fact manner. When she asked him if he was planning to stay here long, he shrugged.

'I know how it is. I was on a wanderjahr myself two years ago,' Keiko Sasaki said, and listed several cities, including Rainbow Bridge. She mentioned people she had met, places where she had worked. He nodded and smiled as she talked, wondering if this was a test, if she was trying to trick him into revealing that he knew less about Rainbow Bridge than he should.

'Of course, it was easier then,' she said. 'There are almost no flights between Saturn and Jupiter now, what with the fear of war. You must be worried about getting home.'

'Not really.' Mention of the war made him wary. He sucked tea from his bowl, picked a stray bit of twig from his teeth and set it in the saucer.

Keiko Sasaki sipped her tea too. At last, she said, 'You met Zi Lei at the Permanent Peace Debate, I think.'

'We first met when we worked together. We live in the same building.'

He was wondering if Keiko Sasaki had been following him.

'You know that she is not well. She works too hard. She worries about war. And she is not taking her medication . . . Did you know that she is schizophrenic?'

He shrugged because he didn't know what to say.

'I'm Zi's friend, Ken. I'm also her health worker, appointed by the city to monitor her welfare after she self-harmed herself two years ago. She is supposed to be taking part in a programme of cognitive therapy designed to help her analyse and deal with her anxieties and fantasies, and she is also supposed to be taking medicine to counteract a serotonin imbalance. At present, she is doing neither because she claims that she is in the middle of a period of intense creativity,' Keiko Sasaki said. 'She has the right to make that decision of course. I can only advise her. But while she's usually amenable to reason, right now she is in a manic phase and is very vulnerable. And the current situation is feeding her fantasies.'

'The current situation?'

'The fact that we may at any moment be at war.'

His suspicion that this wasn't really about Zi Lei, that the woman was some kind of peace officer, hardened into certainty. He had been told that there was a high probability that he would be discovered. It had been emphasised over and again during his training, and he'd spent every waking moment after entering the city wondering if he was being watched by people who knew that he was not who he was pretending to be. A constant state of anxiety and suspicion, of always wondering if passers-by were watching him, if the ordinary exchanges with people at work, in the green markets, and with his neighbours in the apartment block were more than they seemed. A constant low-level dread; constant analysis and self-monitoring. Now all that fell away and he felt that he was sitting at the centre of a great ringing calm. He didn't feel angry or afraid; in fact, he felt relieved that the inevitable had happened. His immediate impulse, which he immediately suppressed, was to ask Keiko Sasaki how she knew, when he had been found out, what had given him away. But until she gave him a clear and obvious signal that she knew all about him, both of them were doomed to play out their roles.

Keiko Sasaki said, 'Zi thinks of you as a friend. An ally.'

'I hope that I am.'

'Good. Then can I ask you to do something? Not to help me, but to help Zi.'

'I can try.'

'If you want to be a good friend to Zi, if you would like to help her, it would be a good idea if you didn't encourage her fantasies. Listen to her, but don't ask questions. Try to talk of other things. And maybe you can keep her away from the Permanent Peace Debate, too.'

'She does good there.'

'It was a useful safety valve when it started, but it's a parody of itself now. It's become the focus of malcontents and fantasists. A place where they can let their emotions run away and elaborate their paranoid fantasies. In some cases that's just what they need. But in Zi's case, encouraging her fantasy, which is what happens every time she gets on that stage and gets people to hum along, isn't good for her at all. She doesn't see that people make fun of her. She only sees what she wants to see. She sees validation. And that drives her deeper into her fantasy, and increasingly alienates her from ordinary life. At the moment, she's so deep inside it that she won't even talk to me. She thinks I'm some kind of spy or enemy agent trying to prevent her straightening out the vibrations. But she talks to you, she likes and trusts you, and that's why I'm asking for your help.'

'I'll do everything I can,' he said.

After a moment Keiko Sasaki returned his smile. 'Zi needs friends. And if you can be a true friend to her, you'll also be a friend to me.'

'We can talk again,' he said from inside his great still calm. He knew that they were talking in plain code. Zi had nothing to do with this, except that she was the excuse for contact.

'I'd like that,' Keiko Sasaki said. 'You're a good person, Ken. I'm sure we have much to talk about.'

He considered his options as he walked to his apartment. They had made clear to him that they knew what he was. They had the power to end the game at any time. It was quite possible that they knew all about his hard work, all the little tricks and traps he had set up, but he couldn't check anything because they might have set traps of their own. And he couldn't abort the mission, either. His controllers could recall him, but he couldn't reach out to them for help. Which meant that he had just two options. He could try to drop out of sight, leave the city and live a fugitive existence, flitting between untenanted habitats and shelters, erasing all trace of his presence each time he moved on. It would allow him freedom of movement, but it would limit his sphere of action, reduce the number of targets he could strike to those few outside the city. Or he could stay in the city and continue to play the game. Keiko Sasaki could try to play him, and he could try to play her while continuing to make his plans to hit the most important targets that he had been assigned.

The second option seemed better. He had much useful work still to do before the Flower of the Forest arrived. And soon after that there would be so much confusion that surely he could slip away, and perhaps he could take Zi Lei with him. The thought of escaping with her comforted and calmed him.

Meanwhile, he had to pretend that things had not changed. He went to meet Zi Lei at a bar in the long park that slanted in the upper part of the city. It was built on a platform perched in a big redwood tree. He swarmed up the steep ropeway and there she was, sitting at the tiny counter, and he felt his heart lift and turn as he sat happy and breathless beside her.

6.

It was generally agreed that war was imminent. The Brazilian flagship, the Flower of the Forest, was due to arrive in the Saturn System in only a few days, and a smaller, unidentified ship was following close behind. Meanwhile, the singleships, tugs and drones belonging to the Pacific Community and to the Brazilian and European joint expedition flew unchallenged everywhere around the moons and rings of Saturn, and the life-support, communications, and transport systems of every city were under attack.

One day, Paris's net fell over completely, and rioting broke out in several places before it was restored. Many people, including every notable scientist, gene wizard and environmental engineer, received messages asking them to surrender. Brief blackouts rolled through random sectors of the city. Five per cent of the output of its fusion generators had been diverted to the ancient electrolysis facility to supplement oxygen production by the microalgal cultures, whose productivity had fallen to sixty per cent of optimum values. The virus infecting the crop plants in the city's farms had been identified, but it had mutated into several different strains and there was still no effective cure.

War fever tightened its grip on the city and its population.

Everyone was issued with an emergency breathing kit: a small air cylinder attached to an inflatable helmet with a self-sealing neck ring. In theory, anyone caught in a part of the city that explosively decompressed could pull the helmet over their head and twist the valve on the cylinder, giving them two minutes to find shelter. In practice it was all but useless. Explosive decompression was not a trivial event like a plumbing accident or a tyre puncture. In a large space like the city's tent it would create an instant hurricane blast. People would be knocked off their feet, struck by flying debris, blinded by fog as water vapour precipitated out of thinning air. People not immediately rendered unconscious or injured by falls or flying debris would probably be too dazed and disorientated to pull on their breathing kit, and even if anyone managed that, they would suffer decompression bruising over their entire body, quickly followed by death caused by sudden exposure to temperatures low enough to freeze oxygen.

But in what everyone was learning to call the current situation, panaceas like the emergency breathing kits assumed totemic significance completely out of proportion to their actual usefulness. Wardens appointed by the mayor's office were given the power to do stop checks on anyone at any time, to make sure that they were carrying their kits, to ask them to account for their movements. The wardens wore red armbands and carried plastic 9mm pistols and shock sticks that the city's manufactories had stamped out from designs more than a century old. They guarded every transport hub and the entrances to every public building and apartment block, patrolled the markets and parks, and stood at the barricades which had been erected at every major intersection in the city.

Because he was a visitor caught up in the city's self-imposed siege, Ken Shintaro was challenged by wardens at almost every checkpoint. In the feverish climate everyone was suspect to some degree or other, but non-citizens were top of the list. So far the city's council had not acted on calls for their internment, but many of the wardens seemed to think that they were just one step away from being enemy combatants, and several times Ken Shintaro had been roughed up or strip-searched in public by these zealous guardians of the city's new regime. Parisians, having set themselves up as the symbol of resistance to Earth's three major powers, were growing increasingly bitter about those cities like Camelot, Mimas or Xamba, Rhea, not to mention almost all the cities and settlements in the Jupiter System, whose populations had voted to declare that they would offer no active resistance to any incursion. Of course, Paris's population could easily disperse amongst the hundreds of empty refuges and oases scattered across Dione, but evacuating the city would be as bad as capitulating to the enemy; they could retain their sense of defiance only by staying where they were, and that meant suffering a constant fear of attack, massive casualties, and defeat, and at the same time denying that defeat was an option.

So they had made themselves sacrifices laid on the altar of their principles. Citizens had to be eternally vigilant, eternally suspicious of their neighbours, alert for any sign of panic, disaffection or disloyalty. Every outsider was a potential enemy, as was anyone who ventured any kind of opinion that contradicted the common mindset that gripped the population, or complained, however mildly, about the privations, or had in the past offended someone who now had been given authority.

Ken Shintaro endured the constant low-level harassment with stoic good humour. A bemused smile; a benign vagueness when challenged; an unquestioning eagerness when asked to agree with some patriotic declaration. Behind this mask, the spy had to stay vigilant, constantly self-monitoring himself, making sure that his expression was always pleasant and his attitude helpful, forcing himself to seem as rabidly enthusiastic during the evening rallies as everyone around him. It had been easy to pretend to be like everyone else when everyone expected him to be like them, but now that everyone's behaviour was in some degree abnormal he had to work hard to make sure that he did or said nothing suspicious, and he sometimes wondered what it might be like to shed his mask and let himself go.

Soon, when the war started, he would have his chance. Meanwhile, he had to pretend to be as crazy as everyone else.

In order to protect the city's freedom, habeas corpus had been suspended, the city's council had been given emergency powers by popular vote, and the council had granted the mayor, Marisa Bassi, the kind of absolute authority that would make most dictators weep with envy. Strict food and water rationing was introduced. Ordinary life was displaced by emergency and safety drills, classes in weapon handling, street fighting and first aid, and work in the volunteer labour brigades that were constructing barricades, hedgehogs, shelters, pillboxes and trenches inside and outside the city. Participation in all these activities was mandatory, and although attendance at the rallies held each evening in the main park was not, almost everyone in the city who hadn't been assigned to some duty elsewhere turned out anyway, packing the park from edge to edge, listening to poets declaim, musicians play, and mixologists perform, all this building up to the concluding address by Marisa Bassi, who each and every night whipped the crowd into a patriotic ferment.

The theme of the mayor's speeches was always the same. No surrender. They will not pass. Get out of our sky. An ardent defiance and aggression backed by patriotism and naive enthusiasm rather than any real military strategies or capabilities. The city's ground defences extended for several kilometres around its perimeter but they were rudimentary and unsophisticated, and although the squads of volunteers who practised hit-and-run guerrilla tactics or manoeuvred on trikes, rolligons, flying belts and platforms out on the plain to the north and east of the city looked impressive, they were poorly armed amateurs who stood no chance against experienced marines and fighting drones. The city's much-vaunted defence system, the missiles and rail guns hidden in bunkers on the surface, the smart rocks and killer satellites in orbit, weren't much better, as incursions by enemy ships had already proven. And once the defences fell over, the city would have to fall back on twentieth-century techniques of trench and street warfare to counter troops armed with twenty-third-century technology.

But although Paris couldn't possibly survive a sustained attack for more than a day or two, the few realistic voices in the debate about war and the practicality of defending a tented city were drowned out by the clamour of the mob. A sense of barely suppressed hysteria heightened the city's daily life. Children played war games and raced around everywhere more or less unchecked; some formed gangs that supplied wardens with food and drink and ran messages or small errands. Adults were gripped by the same excitement, but despite their public declarations of loyalty and a willingness to fight to the death most people were scared and upset and apprehensive. There was an increased awareness that the city's tent and ancillary domes were no more than fragile bubbles of light and heat and air in an immensity of freezing vacuum. Although everyone was supposed to be in a constant state of alert, people drank more and took more drugs, quarrelled, brawled, and indulged in reckless and sometimes public promiscuity.

Two days before the Flower of the Forest was due to rendezvous with its sister ships around Mimas, Marisa Bassi declared martial law.

The first Ken Shintaro knew of it was when his neighbours woke him at six in the morning, banging at his door, shouting, demanding to be let in. He scanned the room to make sure that nothing was out of place, unlocked the door. Several people crowded in at once, led by AI Wilson, the man who organised the apartment building's maintenance rota.

'When did you last see Zi Lei?' AI Wilson said.

He had been trained to tell the truth whenever it didn't conflict with his mission. He said truthfully, 'Yesterday.'

A woman was looking in the shower stall. A man was rifling through the closet. Another man was fingertip-searching the sleeping niche. All the people in the room were wearing red armbands. He could feel their excitement and hostility. They gave him hard looks. They were clearly ready to do him harm. His heart beat a little faster and his scalp prickled. The cool air tingled over every square centimetre of his skin. A man standing in the doorway said, 'Why did you change your lock, friend? The pass key didn't work.'

Another rule from his training: if you are asked an awkward question, you do your best to ignore it. Pretend that you haven't even heard it. Change the subject. He said, 'Has Zi done something wrong?'

The man in the doorway said, 'That's our business. And you should put some clothes on.'

'I was sleeping.'

He moved and reacted slowly and tentatively, his eyelids drooping as if he hadn't yet shaken off sleep, but he was fizzing with barely contained energy, had already worked out what to do if it came to it. Disable AI Wilson by chopping him in the throat and step past him and kill the man in the doorway, with his grabby gaze and scrap of beard under his lower lip like a pubic graft. Break his neck and then do the others. He could see it very clearly for a moment, and realised that he had shifted his stance, ready to act. Luckily, none of the intruders noticed.

'Maybe we should take him in,' the woman in the shower stall said.

'He isn't on the list,' AI Wilson said.

'He's from Rainbow Bridge,' the woman said. 'Lots of peaceniks there. They collaborated. They let those people into their city. They started this.'

Al Wilson ignored her. He had a finicky, harassed manner, as if he was surrounded by obstructions that must be navigated with infinite care. He said, 'We need to find Zi Lei. You're a friend of hers. Perhaps you know where she is. Where she might be.'

'She isn't here.'

'You can't be as dumb as you look,' the man in the doorway said.

'Drop the act and tell us what you know.'

'I don't know where Zi is,' Ken Shintaro said, giving the man the innocent look he practised every day in the mirror, like all his expressions.

'What is this about?'

'It's about treason,' the man examining the sleeping niche said. He was kneeling now, running his fingers under the lip of the niche.

'It's for her own safety,' AI Wilson said.

'The crazy bitch has gone to ground,' the man in the doorway said. 'If we find out you know where she is, we'll back for you.'

'If you find out anything, let me know,' AI Wilson said weakly. His seniority made him the leader of this little gang, but it was clear that the man in the doorway would take over if there was any trouble.

Ken Shintaro said, 'Is this for her safety?'