"Isolate your data desks from the central processing," Stillich said rapidly. "Do it now." now."

The staff hurried to comply.

Pella said, "Some of the drop-outs are at this end. But the transmitting stations are falling silent too. Port Sol-oh, wow, Mars just went. This is system-wide. Spreading at lightspeed, I think."

"Tell me what's doing this, Number One," Stillich said.

Pella's a.n.a.lysis was admirably fast. "Viruses," she said. "Semi-sentient. Voracious. They're just eating their way through our data stores, turning everything to mush. They seem to be targeting AI nodes particularly. It's a smart plague, and it's. .h.i.tting us right across the system. They must have ridden in on the laser signal right after that warning-" Her data desk turned black. She sat back, disbelieving.

One man fell back from his station, clutching his chest. His colleagues rushed to help.

Stillich murmured, "Artificial heart. Anybody with implants of any sophistication is going to suffer."

Kale rammed a fist into his palm. "So they knock out our command and control before their ships even get here. And our people are no doubt already dying, as hospitals fail, and flitters fall out of the sky. d.a.m.n, d.a.m.n."

"Captain, we're going to need to get to the surface," Pella said.

Stillich stood. "Yes. Take what you need. I hope the elevator is stupid enough not to have been infected, or it will be a long climb."

Kale growled, "Why the surface?"

"We have some systems up there that will still work. Those optical-fibre links we laid down are pretty dumb. We robustified the planet, remember? Although we didn't antic.i.p.ate this." this."

"And what about the warning?" Kale asked. "Why issue that now? Their ships are a week out. You think that was referring to the viruses?"

Stillich frowned. "'Take cover ... Flee the cities and the domed colonies ... Take your children; take food, water, power and air'. Sounds like more than a virus to me."

"They're hitting us with something else, then. Other than the ships. Lethe. Lethe. Listen, Stillich. Leave a skeleton crew down here. I want you to isolate that smart plague and fire it straight back at the rebels." Listen, Stillich. Leave a skeleton crew down here. I want you to isolate that smart plague and fire it straight back at the rebels."

Pella said, "Maybe that's why they're sending manned ships. Proof against AI viruses. Surely they'll be shielded against their own weapons-"

"Then send them whatever else we've got too, with my best wishes."

Stillich hastily a.s.signed some of his crew to carry this through. Then he hurried out after Pella and the Admiral.

They came up in the middle of Hyde Park. Under a clear August afternoon sky, they were military officers in gaudy uniforms, tense, sweating, armed, loaded with data desks and comms gear, emerging from a hatch in the green gra.s.s. Pella and the others immediately got to work setting up field comms stations.

Stillich looked around, trying to take stock. The bunker entrance was near the south-west corner of the Park, and through the trees he glimpsed the ruin of the Albert Memorial. The boundary of the Park wasn't clear, for parkland and oak forest covered much of London now; like most of Earth's cities it was like a garden from which buildings towered, needles so tall they penetrated a scattering of cloud. Above all that was the usual furniture of the sky, the contrails of descending s.p.a.cecraft, the glittering sparks of offworld infrastructure.

But as Stillich watched one of those tremendous buildings quivered, and shattered gla.s.s sparkled from its face. Even the buildings needed smartness to stay up. And today the Park was crowded, and getting more full a" the time. People walked in carrying children, or bundles of belongings in cases, sheets and blankets. Some were trailed by serving bots, but many of these looked as if they were malfunctioning, confused.

There was a flash in the sky, like a high explosion. People ducked in unison, cowering from the sky. Moments later a distant sonic boom rumbled.

"It's that d.a.m.n Alphan warning," said Admiral Kale. lilt's scared them all out of their homes. But this is a city of millions. Where are they supposed to go?"

Stillich said, "That warning was sent by planetary colonists. They live under domes, in towns of a few hundred, tops. I've seen them. The Empress was relying on their consciences to have them spare the cities. But what do they know of cities? Maybe they can imagine conditions on Mars or t.i.tan. How can they imagine imagine this?" this?"

Kale said, "I wish there was something we could do for these people. Organise them. I feel helpless standing here."

"We'll have to leave that to the civilian police," Stillich said.

Now people were raising their faces to the sky. Stillich looked up.

The bright blue air was full of sparks that flared and died. And now there was another streak of light that cut across the sky, and a rippling boom of shocked air. Beyond that a broader explosion unfolded silently, like a flower.

"That," said Kale, "looked like a nuclear weapon." said Kale, "looked like a nuclear weapon."

"Sirs." Pella called them over. "We're getting some joy. The optic-fibre net is mostly intact, and some of our data desks stayed free of the viruses. The information flow is patchy. We've sent up another couple of recon satellites to replace those we've lost-"

"d.a.m.n it, woman, get to the point. What's happening to us?"

"It's the comet, sir. You were right, Captain."

The stray comet, buried deep in the heart of Sol system, had burst, transforming in a flash into a shoal of kinetic-energy weapons-dumb but ma.s.sive, fast-moving, and precisely targeted.

"They've been hitting us off-world," said Pella. "Obviously we're vulnerable wherever there's no decent atmospheric cover. Mars, the big dome over Cydonia. They targeted the Serenitatis accelerator on the Moon, for some reason. There is what appears to be a shoal of the things heading out to t.i.tan, Port Sol-we may be able to intercept some of them-the smart plague isn't helping us deal with this, of course."

"A crude tactic, but effective," the Admiral said. "And Earth?"

The comet bombs had first targeted the off-planet infrastructure. The planet's s.p.a.ce-elevator beanstalks had all been snipped, and orbital power nodes, resource lodes and comms satellites were being smashed. Earthport, the wormhole Interface cl.u.s.ter, had been particularly heavily targeted. In with the dumb bombs there was a scattering of high-yield nuclear devices, emitting electromagnetic pulses to disable anything too small to be targeted individually.

A second wave of the comet-ice bombs was raining down into the atmosphere, targeting power facilities like dams and the big orbital-power microwave receiver stations, transport nodes like harbours, air-, s.p.a.ce- and seaports, bridges, road and rail junctions, traffic control stations.

"There haven't been too many casualties yet," Pella said. "Anyhow we don't think so. Some collateral stuff-where dams have come down, for instance. And the smart plague has. .h.i.t monorails and flitters and orbital shuttles; you have stuff just falling out of the sky, crashes everywhere."

"They're disabling us rather than killing us," Stillich said.

"Looks that way," growled the Admiral. "So they got in through stealth. I should have listened to you about that d.a.m.n comet, Captain. You must be sick of being told you were right."

Stillich shook his head. "It's not important, Admiral. What scares me is what else we have missed. That's been the trouble through this whole exercise. None of us can imagine-" imagine-"

Pella held her hand up, her hand at her ear. "Wait. There's another of their messages coming through." She touched her data desk. The same booming male voice, with its flat Alphan accent, sounded out. " ... free citizens of Alpha system and the inhabited stars have no quarrel with the people of Sol system, but with your government. We mean this final strike to be a demonstration of our capability. Please take all precautions necessary, especially along the North Atlantic seaboard. The free citizens of Alpha system ... "

Pella looked at Stillich nervously. "What 'final strike'?"

There was a burst of light in the west, like a sudden dawn. Again everybody flinched. The light seemed to draw down the sky, too bright for Stillich to look at directly.

"Call a flitter," he snapped at Pella.

'Sir-"

"Do it! Get us out of here. And find a way to get a warning to the Empress in New York."

AD 4820.

S-Day plus 3 Sol system

They hung a huge Virtual globe of the Earth in the lifedome of the Freestar, Freestar, Flood's flagship. The crew watched the disaster unfold, mouths slack in awe. Flood's flagship. The crew watched the disaster unfold, mouths slack in awe.

The Atlantic impactor had been the biggest single chunk of the comet, but it had been as precisely targeted as the rest. It had come down in the middle of the ocean, on a ridge of continental-crust formation about a thousand kilometres south of a small island called Iceland.

From viewpoints on the ground, a particle of light was seen to descend from the sky, touching the water, and then, behind a wall of boiling cloud, a pencil of light shot vertically to the sky.

From s.p.a.ce, as rings of cloud expanded, a fireball blossomed, clinging to the carca.s.s of the planet like a boil. The cloud rings merged to become a solid torus, centred on the fireball, and then more clouds formed at higher level. A shock wave spread out through the cloud layer, a reflection of a ring of waves spreading out across the ocean, a water ripple dragging a wall of cloud with it.

The ripple in the ocean emerged into clear air. It was barely visible by the time it approached the land, at Newfoundland to the west and Ireland to the east. But it mounted quickly as it hit the shallowing bottoms of the continental shelves, water forced up into a heap, a wave with the volume and vigour to smash its way onto the land. All around the basin of the North Atlantic the steel-grey of the ocean overwhelmed the greenish grey of the land, the complexities of coastal topography shaping the water's thrusts. As the Alphans watched, the continents changed shape.

Beya was Flood's eldest daughter. At twenty-five years old she had become one of his most capable officers. She watched the repeated diorama in shock. "I heard garbled reports. In some of those lands around the rim of the ocean, before the wave came, they said there was salt in the rain. You know, when I heard that, I didn't know what 'rain' was, exactly. J had to look it up." She laughed. "Isn't that strange?"

"This is a demonstration," Flood said grimly. "The people of Earth know that far larger impactors have battered the planet in the past, causing vast pulses of death, even extinction. This will show them that we want victory, not destruction-but we hold destruction in our hands. This will work on their imaginations."

"Well, it's working on mine," Beya said. "Dad, I never saw an ocean before. A moon-full of liquid water, just sitting there without a dome! Earth is alive, you can see it, not some lump of rock. And now we've hurt it."

"We were never going to be able to loosen the eight-hundred-year grip of the Shiras without being strong."

"But they will never forgive us for this," Beya said.

"It's necessary, believe me." He reached for her shoulder, then thought better of it. "Any news of the Second Wave, the comet crew?"

"Nothing was left of the comet, it seems."

"Maybe the imperial military got to it. That's one ship I'm glad I wasn't on, I must say." He glanced over, to see the Virtual Earth running through its cycle of trauma once again. "Shut that thing down," he called. "Look, we broke through their outer perimeter without a single loss. In twelve hours we make perihelion, closest approach to the sun. We've all got work to do. Tomorrow, it's Sol himself!"

AD 4820.

S-Day plus 4 Solar orbit

The Thoth habitat was a compact sculpture of electric blue threads, a wormhole Interface surrounded by firefly lights. The surface of the sun, barely twenty thousand kilometres below the habitat, was a floor across the universe. Thoth was over nine hundred years old. And all his long life it had been home to Sunchild Folyon, leader of the little community which maintained Thoth, a legacy from the past, held in trust for the future.

But now the rebel fleet was approaching its perihelion, its closest approach to the sun-and Thoth's most significant hour since its construction by Michael Poole was almost upon it.

After prayers that morning Folyon went straight to the habitat's bridge, where, even through the prayer hours, shifts of sunchildren maintained watch over Thoth's systems and position. The mood on the bridge was tense, for the wormhole into the heart of the sun had been shut down for twenty-four hours already, a time unprecedented in Folyon's memory; maintenance downtimes were usually measured in minutes.

But this was an extraordinary moment which required extraordinary measures, as the Empress Shira had patiently explained to Folyon himself-and as he himself had had to relay to a reluctant Lieserl, deep in the belly of the sun. This was total war. Even Thoth had been infected by the smart plague. Every resource available to the empire had to be dedicated to the fight-and that included even Thoth and its ancient community. So Thoth's...o...b..t had been carefully lifted from equatorial to a higher-inclination plane where the habitat was expected to lie in the path of the invasion fleet; and so the wormhole had, for now, been shut down.

The sunchildren had fulfilled their duties to the letter. But Folyon, conditioned since childhood to dedicate his life to a single goal, had found it hard to accept this distortion of his deepest imperatives.

Not wishing to exacerbate the crew's difficulty with his own qualms, he left the bridge and made for the observation deck. As so often, he dealt with his troubles by immersing them in the healing light of the sun, giver of life.

The sun was a flat, semi-infinite landscape, encrusted by granules each large enough to swallow the Earth, and with the chromosphere-the thousand-kilometre-thick outer atmosphere-a thin haze above it all. The sunscape crawled beneath the habitat slowly, but that slowness was an artefact of scale, a collision of human senses with the sheer bulk of the sun. In this free orbit around the sun Thoth was actually travelling at five hundred kilometres a second. Folyon knew how privileged he was to spend his life in the orbit of the mighty star, the physical and philosophical core of human culture. At the prayer hours he would look away from the sun's processed light to the distant stars, and he imagined every human eye, even across interstellar distances, turned to the sun, towards him.

And he wondered how many of those observers even knew of the habitat's existence, or its purpose.

Deep below the habitat, tracking its...o...b..t, the tetrahedral Interface of a wormhole, linked to the mouth tended by Thoth, was suspended in the body of the sun. Searing-hot gas poured into its four triangular faces, so that the Interface was surrounded by a sculpture of inflowing gas, a flower carved dynamically from the sun's flesh. In normal times this solar material would spew from the wormhole mouth cradled by Thoth, to dissipate harmlessly. Thus the wormhole was nothing less than a crude refrigeration mechanism, by which solar heat was pumped away from the fragile human-built construct that housed the soul of Lieserl, and enabled her to survive in the sun's fire. And it was all for a higher goal. Lieserl was a monitor, sent into the sun to investigate a complex, dark-matter canker that seemed to be building up at the star's heart.

Thoth's purpose outdated even the ancient empire of the Shiras, but, designated as a temple to Sol, it had always been maintained faithfully by the Empresses' lieutenants. Now Lieserl's wormhole was to be used as a weapon of war-but even this remarkable incident, Folyon knew, was but an episode in the greater history of Thoth and Lieserl.

A sunchild touched his arm, a young woman. His thoughts, as so often, had drifted away from the here and now. Sunchild Mura said, "The time is close, sun-brother."

"All goes well on the bridge?" He felt anxious.

Mura was empathetic for a girl of her age and she knew his moods. "Everything is fine. You would only distract them all, forgive me for saying so, sun-brother."

He sighed. "And so we go to war."

"They tell me you can see it from here. The fleet." She scanned around the sky-every photon pa.s.sed by the observation deck blister was heavily processed-and pointed to a cl.u.s.ter of starlike points, far away above the sunscape. "There they are."

The lights grew in size and spread apart a little; Folyon saw now that they were splinters, like matchsticks, each with blazing fire at one end. "An enemy fleet from Alpha Centauri, come all the way to the sun. How remarkable."

Mura counted. "Five, six, seven, eight-all accounted for. And their GUT drives are firing./I This was celestial mechanics, Folyon knew; if you entered the solar system from outside perihelion was energetically the most advantageous place to dump excess velocity. "They will come close; the projections of their trajectories are good," Mura said, sounding tense. "And they will come on us quickly. The moment of closest approach will be brief. But the systems are automated-the reopening of the wormhole won't rely on human responses." She hesitated. "Did you tell Lieserl what is happening today?"

"I thought it was my duty," he murmured. "She will remember all this, after all, long after the rest of us are dust. I wonder if they are praying."

"Who?" Mura asked.

"The crews of those ships. For they worship Sol too, do they not? And now we are about to use Sol itself to kill them." He lifted his face, and his old skin felt fragile in the sun's processed light. "Do we have the right to do this? Does even Shira?"

She grabbed his arm. "Too late now-"

The ships exploded out of the distance. And at closest approach solar gases hosed from the drifting wormhole Interface, turning it into a second, miniature sun. Solar fire swept over the invaders. Mura whooped and punched the air. Folyon was shocked and troubled.

AD 4820.

S-Day plus 4 Oort Cloud, outer Sol system

Densel Bel wished he could see the sun, with his naked eye. After all, he was among the comets now, within the sun's domain.

He stood in the dark, peering up at the zenith, the way the ship was flying; he tried to imagine he was rising in some spindly, superfast elevator. A light-week out from Sol, with the ship travelling at less than two per cent below lightspeed, the view from the lightdome of the Fist Two Fist Two was extraordinary. All was darkness around the rim of the hemispherical lifedome. The only starlight came from a circular patch of light directly over his head, crowded with brilliant stars, all of them apparently as bright as Venus or Sirius seen from Earth. He knew the science well enough; the starfield he saw was an artefact of the ship's huge velocity, which funnelled all the light from across the sky into a cone that poured down over his head, even from stars directly behind the ship as it flew. was extraordinary. All was darkness around the rim of the hemispherical lifedome. The only starlight came from a circular patch of light directly over his head, crowded with brilliant stars, all of them apparently as bright as Venus or Sirius seen from Earth. He knew the science well enough; the starfield he saw was an artefact of the ship's huge velocity, which funnelled all the light from across the sky into a cone that poured down over his head, even from stars directly behind the ship as it flew.

And meanwhile the stars he was able to see were not the few thousand visible in solar s.p.a.ce by the naked human eye. His extraordinary speed had imposed a Doppler effect; the stars behind had been redshifted to darkness, while the 'visible' stars ahead, including the sun, had similarly been blueshifted to obscurity. But conversely red stars, giants and dwarfs pregnant with infra-red, now glowed brightly, crowding the sky, a hundred thousand of them, it was thought, crammed into that tight disc.