The universe was about to change forever.

Alone on the bridge of the Shepherd Moon, Rix gazed at the asteroid on the screen, not at the Earth below. All his life he'd waited for this moment—he'd been born to it, almost; the final revenge against the Sapes. He felt his stomach churn with hatred. The people on Earth would have noticed the huge rock plunging towards them by now. But there would be nothing they could do. The asteroid was only minutes away from hitting the planet dead centre. It was hurtling down against the direction of the planet's orbit, so Earth's velocity would combine with Shiva's to make the force of the impact even greater. A head-on collision of two mighty worlds.

The final numbers from Zeus appeared on a screen. Rix fed them into the ship's AI.

The final course correction, the last burn of the engines on the surface, and it was done. The trembling in his hands ceased, his stomach suddenly settled. There was nothing more to do, and nothing in the world that would stop the deaths of billions.

Rix's smile broadened as he started programming the AI for self-destruction. It wouldn't be needed once Shiva had entered its final course. Even if those prisoners had managed to avoid being thrown into space then there would be no way they could control the engines on the asteroid that were now pushing it to its final collision speed.

Thirty kilometres per second.

Fast enough to kill every stinking Sape soul on the planet.

***

Maddy wished Marshall would stop breathing down her neck. The man was hardly allowing her space to think, and she needed to think a lot. The lock on the door was sealed with a complex code, more complex than she'd anticipated, and unless he moved back a little her fingers couldn't obey the commands her brain was trying to give them.

Then she managed to make something work, and the door opened. Marshall charged forwards, leading the way out of the room. Maddy followed him, a little more carefully. By the time she looked again into the short corridor leading to the lounge and the bridge, Marshall was engaged with fighting a male Helot who had been lurking in the engineering bay. He was putting up a determined fight. Marshall had a wounded left arm, but that didn't seem to affect his enormous strength. The two bounced off the walls, a desperate mass of muscle and ferocity barring Maddy's further progress towards the rest of the ship.

A noise made Maddy turn, raising her gun. A female Helot was there, staring at the group, mouth open. Maddy was the closest to her. Her open mouth began to make a sound that might shortly turn into a scream. Maddy lunged towards her and the woman turned and ran.

Marshall had concluded his fight with the Helot, thrusting him against the wall of the corridor and firing his weapon point bank at his head. Maddy pushed past and looked out into the lounge.

'No one here!'

Marshall walked into the deserted lounge, where the holovision was blaring a news report about the arrival of an asteroid near Earth and how it represented a new form of mining technology.

'What do we do now?'

'Stop the asteroid!'

She stared at the door that must lead to the bridge. It would be locked, of course, encrypted, more complicated than the door to the engineering bay. I need a fone, she thought. And a miracle.

'Do your best,' said Marshall, and actually smiled and clutched her shoulder for a moment.

The man was right, of course. The Earth was at stake, although what she was supposed to do if she opened the door was beyond her. She moved across the room to examine the lock. Marshall remained in the lounge on guard.

One glance at the lock convinced her it was hopeless: someone had sealed it from inside and without a bag of probes and a decent fone there was no way she would be able to open it. There had to be some other way...perhaps return to the engineering level and see if they could interfere with the ship's AI somehow—but it was the asteroid she wanted to stop, not the ship itself.

A movement beside her made her duck. A steel harpoon embedded in the wall with a thump that must have alerted anyone on the bridge. She dropped and turned, casting about for some sort of cover.

Marshall had dropped to one knee and was firing his gun. Plasma bolts ripped through the air and slammed into the ship's hull. Another klaxon started roaring as the hull was breached in several places. The sound filled the interior of the ship. Somewhere an AI added its own warning to the alarm.

On the other side of the room Maddy could see Gibbon loading a harpoon. Marshall's shots had melted the wall around the man's cover; obviously the stunned Helots had recovered their senses and come up to attack.

Someone grabbed Maddy and lifted her. Monk snarled in her face, pushing her roughly up against the bulkhead, arm across her chest.

'You can't win!' he hissed.

Maddy tried to shove him away, but he had the strength of a Helot born to labour. Her gun was in her right hand; he had used his other hand to grab her wrist and twist it, trying to make her drop the weapon. It felt as if her bones would snap. The man's face was close to hers and she tried to grab his hair with her free left hand, but he used his elbow to keep her arm too far away.

Then Monk went limp, falling away to the floor. She looked over his body at Marshall, who had fired in her direction. The plasma bolt had narrowly missed her as it passed through Monk's body.

'You all right?' Marshall asked.

There didn't seem to be any remaining opposition. Gibbon lay slumped where he'd been shot by Marshall. Any other opposition seemed to have disappeared. The klaxon continued to scream.

'I can't get through this door!' she said. 'We have to do something else.'

Then the door of the bridge opened. Maddy, beside it, turned to look and just managed to slide away as Rix's hand reached out to grab her.

Marshall raised his gun to shoot, but only a dull click came from his weapon. He cursed and threw the empty gun towards Rix and then followed the trajectory towards his opponent.

Rix's gun roared. Marshall fell, inertia causing his body to slide across to Maddy's feet.

She jumped away, using all her strength in the mock-Lunar gravity to bound to the other side of the room to where the sofa offered minimal cover. She managed to duck behind it as another bullet tore past.

Nothing more. Maddy remained hidden, straining against the ululation of the klaxon to hear any sound of approaching feet. On the carpet and in the light gravity, it would be almost impossible to hear approaching footsteps even without the alarm's noise. She put her head on the floor and tried to peer under the sofa to see if she could spot the man's feet.

'Get up,' came a voice.

Nothing for it. Maddy rose and stood with the sofa between her and Rix. He had a pistol pointed at her head.

Maddy aimed her gun at the man's chest. All he did was smile, his finger on the trigger of his own weapon.

'Very brave,' he said, 'but it's too late.'

'Please don't do it,' she pleaded, the words sounding almost child-like in their anguish. 'Please...it's...it's the Earth.'

It's the centre of the universe. It's history and culture and beauty and art...

Rix just shrugged. 'Too late, as I said.' From the bridge came an electronic howl and a flash of blue light. The man smiled. 'There goes the AI.'

Maddy knew he was telling the truth: she knew the dying bray of an AI as it fused. Rix must have sabotaged the controls.

'Shiva is on its way,' he said. 'There's nothing to be done.'

She kept her gun trained on him, but it trembled slightly in her hands.

'You...you...' A tear started on her cheek. 'Stop it! You can still send a signal using Message Stick! I know you can, I...'

There was no time to explain. She had to get to the MS controls, find some way to send a countermanding signal to the engines on Shiva. It was a stupidly useless thing to do, a blind luck chance that she could make it happen, but she had to try.

'Out of my way,' she said.

'Go to Hell.'

She took a step from behind the sofa but he moved to step in front of her.

'I can save the Earth,' said Maddy. 'Please. You don't have to—'

He brought his right hand in, holding his gun, to aim at her.

Maddy fired.

The ceramic bullet howled from the barrel into Rix's chest, boring a hole right through and out his back, to slam into the wall of the bridge. He crumpled to the floor.

Maddy dived for the bridge, clearing Rix's corpse in one bound, and stared at the wrecked AI. Smoke coiled in the air from fused electronics. The main panel was stone dead.

Against the far bulkhead was what she recognised as the MS controls. All it would need was a signal to the engines on Shiva to alter course. A specific direction wasn't necessary, just somewhere other than the planet below.

But those controls were also dead. Rix had killed them when he killed the ship's AI. Nothing worked on the panel board; even the main MS power cubes were down. Without them the Message Stick system was as dead as Rix.

How do you stop a trillion tons of iron?

She slammed her hands on the panel and stared at the main screen. Shiva was smaller now, curving in a perfect mathematical arc down towards the waiting Earth. There was no telling how much time was left. The bridge was a dead lump of metal and glass.

I can't do it. I can't do anything.

Six deep breaths while she stared at the plunging asteroid, her knuckles white on the panel. Then she pushed a lock of hair away from her face as the klaxon roar of the air leak alarm reasserted itself. It had been sounding all the time, but forgotten in the struggle.

She couldn't do anything to save the Earth.

But I can save Geranium.

The girl was still on the asteroid, and had only a few minutes to live, unless Maddy could do something, even if it was no more than die with her and the rest of the world.

She left the bridge and headed for the dinghy bays. There was no one around, just the dead bodies in the lounge. She didn't stop to look at them for signs of life.

A hatch in the bulkhead hung open. Perhaps a crew member had already taken refuge there, might be waiting for her with a weapon, but there was no alternative. She stepped through into the space beyond, gun held out ready. There was no one in the cramped docking bay beyond. She closed the hatch and hit the lock mechanism and felt herself go light: the centre of the spinning ship; micro-gravity. It was dark in the space for a second, then the AI, detecting her presence, switched on the lights.

The klaxon of the air leak warning was duller here, but still present. The corridor had its own air supply that had not yet been compromised. A waft of air conditioning struck her heated face as she began a slow crawl through the access tunnel. After ten metres the tunnel ended in another hatch, a properly sealed one that indicated an airlock to the dinghy bays.

She opened the hatch and climbed through to the first dinghy. The small ship lay outside the hull of the Shepherd Moon, with a short tube to access it. She slid along this into the tiny craft.

All was silent as she sealed herself in.

'AI.'

'Online.'

There was the miracle she needed. If the dinghy had been secured with a code there was no way to launch in time.

'There's a ship on the asteroid Shiva. Do you have the location of that ship in your memory?'

'Yes.'

'Take me there.'

'The asteroid is in motion towards the Earth.'

'Then take me there quickly!'

The little boat jolted slightly as the hardlocks were disengaged. Maddy felt herself pressed back in her seat as the dinghy pulled away from the Shepherd Moon and coasted over to the asteroid.

Through the dinghy's window the double-disc/sphere shape of the Shepherd Moon struck her as odd, then she realised it was the first time she'd seen the ship from outside. As a prisoner just an hour or so ago there had been no chance to observe the vessel. Now it looked such a small thing, an ungainly yellow and white craft, trailing a long but useless MS tower behind it.

'Other vessels are detected,' said the AI.

Maddy looked to the right of the Shepherd Moon as something flashed briefly in the sun. Another object followed it, and another. The small objects careered into the ship almost before Maddy could register their presence.

The Shepherd Moon vanished in a brief slam of explosion. Another burst and another as the other objects collided with the few pieces left.

Someone had had the presence of mind to destroy the ship, but too late. Shiva could not be stopped so easily.

They were all gone, then, even those Helots who might have survived the fight, who were hiding somewhere on the ship. And Reed was gone, and Marshall, and even the man Rix who had started it all. No survivors.

Only Maddy, tumbling away in a small dinghy towards more death and destruction.

***

Geranium roused herself from the floor. How long had she been lying there? It felt like ages since the Serf had gone through the airlock door. She glanced through the window, but the outer door was closed and the body of the Serf was not visible.

A horrible thought gripped her that the man was still alive somehow, prowling around, waiting for her to emerge from the ship. But of course not—that wasn't possible. He'd asphyxiated on the iron surface of Shiva, gasping and choking his life away, his body pounded by cosmic rays, his eyes filling with blood.

She had killed him.

For a moment she imagined herself arrested, found guilty of murder, and having to face the wrath of her parents as they accused her of ruining the family name, of crippling her father's reputation, of bringing disgrace to the deForêt-Bassyngthwaightes. Her little brother and sister would hate her too, which was even worse.

There was no pride in the realisation she had fought for her life and won.

The comlink beeped. 'Geranium!' It was Maddy's voice, clear but strained.

'Geranium here! Are you all right, Maddy?'

'Yes. No. Listen. The others are dead. Is anyone with you?'

'No! He's...not. I'm alone.'

'Good. I'm on my way there. A few minutes.'

'The others are dead?'

She clutched the edge of the desk until her knuckles went white.

'Yes. Look, that doesn't matter right now. I have to get you off the asteroid.'

'The ship can't fly. The AI's still locked.'

If Reed was dead, then the password had died with him.

'Are you able to get into a viable space suit?'

She glanced over at the helmet that still hung on its rack next to the airlock. Drummer's helmet was there too, red against her helmet's slate grey. She tried not to stare at it.

When she looked back at the main window, something appeared on the horizon: a dazzling line of brightness that illuminated the crags and ridges of the asteroid even more than the Moon. Geranium thought it was the Sun, bringing a day to Shiva that it had never experienced.

Maddy was talking to her, telling her she would land the dinghy as close as possible to the ship. But Geranium would have to trek across the surface. Above all, Maddy kept saying, she had to hurry.

Geranium was already slipping the helmet over her head. The stifling sensation returned and for a moment she gagged, but whether it was the claustrophobic helmet or the memory of her fight with the Serf, she couldn't say. A few moments of deep breathing calmed her.

The AI's voice informed her that the suit's situation was at optimum; she switched back to the ship's comlink so she could hear Maddy.

'Get out of the ship,' Maddy said. 'I don't want any time wasted when I land. We'll only have a moment.'

'Why?'

The bright line on the horizon expanded, filling the whole scene. It wasn't the Sun—if it had been she would not have been able to look at it. As it grew there seemed to be darker areas visible. Swirling white shapes, large areas of blue. It rose further to show its round shape, a huge, radiant world. What was it? Why was it so close? She'd seen it somewhere before.

Nothing seemed to make sense anymore.

'Geranium! I can see your ship! Get out now! I'm coming down.' Maddy's voice cut through her dazed mind like a laser.

She opened the airlock and stepped inside. Maddy's voice continued in her ears. There were a thousand questions she wanted answering, but the woman seemed to be gabbling away as if she didn't want Geranium to speak.

The outer door opened. Drummer's body was at the foot of the ladder, contorted, one arm stretched out as if reaching for the airlock contact. She didn't look at him, but had to step over him to move away from the ship.

The huge ball of light was even bigger out here, moving visibly across the sky, revealed as a true planet at last. And she knew what it was now: the enormous, vivid Earth. Her home. Continents were clearly visible: Europe and part of Africa.

Why was it this close?

Something dark appeared on the face of the huge planet: a small ship, using its lifters in a fast descent. Geranium stepped towards where it would land. Hurry, Maddy had said. The constant stream of the woman's voice had ceased now she was landing, but Geranium felt it wasn't the place for questions. If Maddy wanted her to focus on being rescued there was a reason behind it.

The dinghy landed fifty metres from the ship. Geranium stepped carefully—she remembered her last experience out on the surface and didn't want to smash into anything, despite the haste that Maddy urged.

'Stop!'

Geranium halted just beside the door of the dinghy. Maddy's face was visible in the small window. She appeared frightened, her face lined and pale. Geranium waited, as the Earth swelled even larger in the sky.