Luther passed the book to Lord Cypher and led the way, his black cloak flapping wildly in the howling gale kicked up by the Stormbird's thrusters. Zahariel followed six paces behind Lord Cypher, flanked by Brother Attias to his right. Six other Astartes, all veterans of the fighting on Sarosh, fanned out around them, their weapons ready. Three other assault squads were deploying from their own transports on the landing platform as well, spreading out in a wide arc to cover the command squad's flanks and rear.

The heavy blast doors leading to the arcology's upper levels had already slid open by the time Luther and his warriors had disembarked, and a large group of green-uniformed Jaeger officers were struggling to reach them through the gale spawned by the drop ships' thrusters. Leading the Jaeger troops was a wiry, sharp-featured officer in smoke-stained flak armour and fatigues.

'Colonel Hadziel,' Luther said in greeting, his powerful voice carrying easily over the roaring wind.

'An honour, my lord,' Hadziel shouted back. One hand was pressed to the top of his helmet to keep it in place, and he squinted into the grit kicked up by the Stormbirds. 'I apologise for not being able to keep you apprised of the situation during the trip, but the rebels have found some way to jam all of our vox transmissions. I can't coordinate with my squads inside the arcology, much less send or receive signals outside.'

'No need for apologies, Colonel. Frankly, we expected something like this.' Luther paused for a moment as the four transports took off with a bone-jarring roar, then spoke into the ringing silence that followed. 'One thing we need to be clear on from the outset, however, is that the rebels are not responsible for this. In fact, as of three hours ago, I concluded a truce with the rebel leaders, and they have agreed to assist us against our common enemy.'

Hadziel and his staff exchanged bemused looks. 'Common enemy, my lord?' he asked carefully.

'Now is not the time for a detailed briefing, Colonel,' Luther said sternly. 'I assure you, all will be made clear once we've gotten this situation under control. Suffice it to say that a cabal of off-worlders housed here at the arcology have hidden themselves somewhere in the lowest sub-levels and are exposing this entire area to the malign effects of the warp.'

To his credit, Colonel Hadziel accepted the bizarre turn of events with surprising poise. He blinked once, and nodded curtly. 'How can I and my Jaegers be of service, my lord?'

'Good man,' Luther said proudly. To a man, Hadziel's staff grinned, their confidence restored. The Master of Caliban beckoned them to fall in around him. 'First,' he said, 'what's the current situation and the disposition of the civilians?'

Colonel Hadziel gestured to a pair of staff officers, who presented a portable hololith table and set it up at Luther's feet.

'For the last few hours, it's been complete chaos,' Hadziel said grimly. He keyed in a number of commands, and a cross-section of the arcology filled the air above the table. 'As luck would have it, the evacuation order from Aldurukh had just gotten underway when the unrest began. As a result, we already had a movement order in place and there were combat squads in the hab levels when the unrest began. Those squads bought us precious time to organise and took a lot of pressure off our checkpoints in the early stages of the riots. Otherwise, our cordon would have probably been completely overrun.'

'How many civilians were you able to evacuate?' Zahariel interjected.

The colonel shrugged. 'Thousands, certainly,' he said, 'but I've no way of determining an exact number of evacuees. We're still trying to let people through, but it's extremely difficult at this point.'

'Why?' Luther asked.

Colonel Hadziel took a breath, considering his reply carefully. 'These riots are much worse than anything we've seen before,' he said. 'We'd thought maybe some kind of disease had taken hold in the hab levels - something savage, like crimson fever or rabies. The last reports we got from our squads in the lower levels reported mobs of bestial civilians attacking every living thing in sight. Gunfire didn't seem to slow them in the least short of a las-bolt to the head. The uninfected civilians are panicking and trying to mob our checkpoints in an effort to escape.' The colonel's jaw tightened. 'There have been several incidents of troops turning their guns on the civilians in order to keep the crowds at bay.'

He hit another set of keys and gestured to the holo-image. 'As it is, I've been forced to give up my initial positions and fall back to level fifteen, where there are fewer access points to cover and I can pass orders using runners.' Almost half of the lower levels of the arcology began to blink red. 'Everything below that level, including all the sub-levels, has been lost, which includes the arcology's thermal power plants, water and air circulation and waste recycling facilities. In purely military terms, we're no longer in control of the arcology.' Hadziel spread his hands. 'We're still trying to save as many civilians as we can, but we've got to check every group and make sure they're clean before we can let them through.'

Luther turned to Zahariel. 'Are there any measures we can take to quickly discern living humans from these walking corpses?'

Hadziel's eyes widened. 'Corpses, my lord? Those were reports from panicked troops. Surely you don't believe—'

'Make sure the checkpoints are issued thermal auspex units,' Zahariel cut in. 'Even a thermal lasgun sight will do. The corpses will have a much lower heat signature than the civilians around them.'

'Well, I…' Hadziel began, then took one look at the Astartes and thought better of his protest. 'I mean, I'll send the word out immediately.'

Luther nodded curtly. 'Very good, colonel.' He paused for a moment, studying the display carefully for a moment. 'At this point, I want you to focus your efforts on holding the checkpoints at level fifteen and to continue evacuating civilians out of the hab levels as quickly and efficiently as possible. My warriors will form into strike forces and will pass through these checkpoints—' He indicated seven strategic locations across level fifteen '—and will advance into the contested areas towards the arcology's power plants and life support centres.'

Hadziel frowned. 'My lord, we have no clear estimates on the number of infected individuals on the lower levels, but it certainly reaches into the hundreds, possibly thousands. They will be drawn to your warriors like blood moths to a wounded deer.'

Luther nodded in agreement. 'That's the idea, colonel. My brothers will deal with the corpses and take the pressure off your troops. Once you've completed relocating the civilian population you'll be able to commit your forces to securing the arcology's lower levels. I want you to assign a liaison officer to each of my teams and ensure that their path through the checkpoints is cleared. That's all for now, gentlemen. We'll speak again once order is restored.'

Hadziel nodded and began issuing instructions to his staff officers, who immediately began to draft the necessary orders. Luther turned away from the Jaegers and motioned for Zahariel, Attias and Lord Cypher to join him several paces away.

'Any word from the rebels still inside the arcology?' he quietly asked Zahariel.

The Librarian shook his head. 'They're having no better luck with their vox-units than we are,' he replied. 'There's no way to know if they've found the sorcerers or not.'

Luther nodded. 'Do you believe Colonel Hadziel's estimate of the number of corpses in the lower levels?'

Zahariel shook his head grimly. 'Not in the least. They must number in the thousands, possibly the tens of thousands.'

'An army of the dead,' Brother Attias said in his hollow, synthetic voice. 'But to what purpose?'