Some had called it the white death, or the underhive pox, or spirit rot. The doctors who tended to the city's ailing aristocracy invented long, complex High Gothic names for it. But by the time old Governor Hugenstein had succumbed, his body a mass of seeping welts, along with his family and most of his staff, it was known simply as 'the plague'.

No one knew how to cure it. Everything from full blood transplants for the super-rich to folk remedies, devised when the city was young, were tried and failed. In desperation, the people looked for a cause - and scores of innocents were burned as pox-spreading political agents or witches. By the time the pyres of plague dead broke the city's skyline, even being uninfected was a death sentence. But no one could tell where the infection came from. And trying to understand it just made it kill quicker.

Some got out. The Administratum offices cut through enough red tape to get the higher echelons to safety. Some of the manufactorium owners made the most of their razor-sharp business sense to buy themselves passage out of Hive Quintus as passengers on fleeing pleasure-yachts or human ballast on smugglers' scows.

Others could have run but did not - the governor had done the most noble thing of his reign and presided over the death of his city. The Adeptus Arbites decided without debate to stand their ground and preserve the Emperor's laws even as the city fell apart. The preachers of the Adeptus Minis-torum stayed, and bellowed the Emperor's praises from temples crammed with desperate infected citizens. But the hundreds of millions who filled Hive Quintus's thousands of layers all wished they had the chance to flee in one of the pitifully few craft that were escaping. Any craft large enough to carry a significant number of people was shot down by orbital defence lasers maintaining the quarantine order against Eumenix - those who escaped did so in a tiny trickle, barely a dent in the massive, doomed population.

That, of course, did not stop larger ships from taking off and being turned into long burning streaks in the sky - more omens of death for the people below. But there were some smaller ships in the city that might run the quarantine blockade. Some spaceports were still operational, and whenever word went round that there was a ship about to launch, hordes of half-dead victims piled up around the launch pads and ship hangars.

Most of the time there were no ships. But as the plague reached its height, on Ventral Dock 31, Cartel Polios managed to salvage a small research vessel just spaceworthy enough to get the House patriarch and his immediate family off Hive Quin-tus. Sure enough, masses of plague victims swarmed against the walls around Ventral Dock 31, held at bay by the private army of Cartel Polios. Shotgun blasts ripped down into the crowds as the ship fuelled and prepped for takeoff. It was perhaps the last hope for anyone to escape the plague.

Hope was the rarest commodity of all. But when a massive explosion tore out a section of the east wall, all hope disappeared.

THE AUTOSENSES IN Sergeant Salk's helmet snapped his pupils shut as the glare of the explosion burst across the east wall. From his squad's vantage point in the ruins of a hab-block like an island in the centre of the heaving plague-infected crowd, he could see chunks of ferrocrete hurled into the air with a massive thunderclap. Pollos's guards were thrown off the battlements and a ripple ran through the crowd as the front ranks were blown backwards by the force of the explosion.

Karrick's demolition charge had done the job. Separated from his squad, Karrick would be lucky to survive to meet up with the rest of the squad, if any of them got inside the spaceport at all. But that didn't matter now. Captain Dreo was dead and Salk was in charge. The squad had secured their target and he understood that if he had to cash in the lives of his battle-brothers to complete his mission, then he would do so.

'Go!' he yelled into the vox and the six remaining Soul Drinkers vaulted from the burned-out windows of the shattered hab-block. They landed in the thick of the crowd and Salk felt festering limbs pushing against him as he sunk into the crowd as if into an ocean. He clambered to his feet and saw the rest of the squad battling against the human tide -Space Marines were a clear head and shoulders taller than the tallest unaugmented man and Salk easily spotted the Marines of his squad: Krin with the plasma gun, Dryan, Hortis, Aean and big Nicias hauling the squad's sole prisoner.

Nicias had been forced to abandon his missile launcher after the mission's bloody early stages, where Dreo was lost, and had fought on with knife and bolt pistol. He had accepted responsibility for hauling the prisoner, head covered and wrists bound, with his free hand.

Salk forged a way through the heaving crowd. Lolling-mouthed, mad-eyed faces loomed from the masses and hands grabbed at him. They were lit by the fires that burned in the hive-spires rising all around like mountain ranges, and the searchlights directing the fire of the soldiers on the breached walls of the spaceport. There must have been ten thousand crowding up against the east wall alone, and Salk could see where they were piled up, living and dead, against the barricades beneath the walls. Salk pushed through them, his power armoured body barging bodies aside. He picked up and threw those in front of him. He didn't want to hurt these people - they could not help the madness of the Imperium into which they had been born - but if they put themselves in his way, he would crush them underfoot. This mission had turned ugly from the outset, and it would end ugly, too.

The crowd surged forward as the front ranks recovered from the blast and began to pour into the breach. Gunfire stuttered from up ahead as the Cartel Polios troops poured their fire into the plague victims that clambered over the rubble onto the landing platform of the spaceport.

A missile streaked down from the closest watch-tower and blew a hole in the surging crowd. Salk pushed against the crowd and burst out into the smouldering crater, ringed with blackened bodies, a short sprint from the yawning breach in the wall. The wall was twenty metres high and several thick, but the charge had torn a huge section out of it. Autogun fire was already spraying from behind the fallen chunks of masonry, with shotgun blasts barking beyond the rubble as Cartel Polios troops hunted down the plague victims that had got through.

'Nicias, Krin, with me!' voxed Salk as he fired a couple of bolter shots at the gaudily dressed Polios troops ducking behind the masonry. 'The rest, covering fire!'

The huge form of Nicias tore out of the crowd beside Salk, followed by Krin. Already some of the troopers had spotted the massive purple-armoured Marines and were directing their fire towards them, rightly singling them out as the biggest threat to the east wall. Autogun fire spanged off Salk's shoulder armour and he returned fire, almost blind, as he put his head down and ran across the open ground towards the cover of the rubble in the breach.

The two Space Marines back in the fringes of the crowd opened up on full auto with their boltguns, spattering the walls with miniature explosions. Troopers on the walls jerked and fell, some tumbling over the lip of the wall onto the barbed wire and barricades below, their bodies mingling with those of the fallen plague victims.

Salk slid into cover as a heavy stubber in the watchtower stitched fire all around him. Nicias was seconds behind him, firing up at the watchtower. There was a missile launcher and a heavy stubber up there, and by now the Polios troops would have marked Salk and his Marines as priority targets.

And with good reason. A spear of white heat ripped up from the open ground behind Salk and the top of the watchtower billowed open, the blast of the plasma impact compressed within the fire-point and incinerating whatever men and munitions were inside. Krin, plasma gun shimmering with haze as the heat rose from its charging circuits, stumbled under the impact of autogun fire from the walls but slid into cover beside Nicias.