Epsilon's civilian pilot came back over the vox at once. 'My co-pilot says he's seeing red flashes to the north, out beyond the perimeter. My starboard engine's been hit. Temperature is spiking! I need to divert and make an emergency landing!'

'Negative, Three-Niner Heavy,' the controller shot back. 'Increase speed and altitude. Do not, I repeat, do not attempt to land.'

Zahariel shook his head in irritation. The civilian pilots always tried to set their transports back down at the first sign of trouble, not realising that turning around and slowing down for landing only made them more vulnerable to ground fire. Thunder reverberated through the room as the combat air patrol roared past Aldurukh's spires, heading north at full speed.

'What are the rebels going after this time?' Zahariel asked as he reached Luther's side.

'A Type II cargo hauler loaded with ten thousand tonnes of promethium,' Luther replied grimly, his eyes fixed on the vox-unit's grille. 'They couldn't have picked a better target.'

Zahariel's eyes widened. Epsilon Three-Niner was, for all intents and purposes, a flying bomb. A direct hit on one of the pressurised promethium tanks in its cargo holds would turn the ship into a massive fireball, scattering wreckage and blazing fuel all over the northern landing zones. He thought of all the fuel substations and warehouses in that sector and tried to calculate the devastation such an explosion would cause.

The vox-unit crackled once more. This time, the deep voice of an Astartes sounded from the grille. 'This is Lion Four; I've got a visual on Epsilon Three-Niner at this time. Stand by.' Moments later, the pilot spoke again. 'Contact! I've spotted a group of rebels operating a lascannon from the back of a civilian truck two kilometres outside the perimeter. Engaging now.'

'Hurry up, Lion Four!' shouted Epsilon 'Three-Niner. We just got hit again!'

Lion Four didn't respond. Seconds ticked by, and Zahariel realised the strategium had fallen silent. Then, moments later, the vox crackled once again.

'This is Lion Four. Target destroyed. Repeat, target destroyed. Epsilon Three-Niner is clear.'

A relieved cheer went up from the Jaeger officers and Legion aides; any victory, however small, was worth celebrating under the circumstances. The Astartes in the chamber received the news impassively and continued with their work. Zahariel took a long breath and glanced at Luther. 'The rebels are getting bolder,' he observed. 'That's the third attempt in the last twelve hours.'

The Master of Caliban frowned thoughtfully. 'We need to push the perimeter out another five kilometres or so, and increase our mobile patrols. Sooner or later they'll realise that vehicle-mounted lascannons are too easy to spot and switch to shoulder-fired missile launchers, which will make our job that much harder.'

Zahariel nodded in agreement. So far they had been fortunate; two shuttles had been shot down over the past two weeks, but none of the larger transports had suffered more than minor damage. Clearly the rebels hoped to interdict all orbital traffic from Aldurukh to the waiting supply ships above Caliban, but Luther was determined to continue operations despite increasingly loud protests from the civilian pilots who were hauling the cargo. Of greater concern to Zahariel was the fact that no new supplies were coming in to replace those being launched into orbit.

'We have four Jaeger regiments in training that are advanced enough to perform basic combat patrols,' the Librarian suggested. 'We could put them on perimeter patrol immediately.'

'What about line regiments?' Luther asked.

Zahariel shook his head. 'All of our combat-capable units have been deployed. Right now the Jaegers are stretched thin.' He paused. 'We have almost an entire Scout chapter ready for action, brother. We could send them out in pairs to patrol the countryside around Aldurukh and hunt down rebel weapon teams instead of calling up the trainees.'

Luther seemed to consider this for a moment. 'If the tempo of rebel attacks increase, I'll consider it,' he said at length. 'In the meantime, set up a patrol rotation for the training regiments.'

'Very well,' Zahariel replied. He tried to keep any trace of exasperation from his voice. Violence had raged across Caliban for two weeks, and the Dark Angels had yet to stir from Aldurukh. He couldn't fathom Luther's reluctance to commit the Legion. Zahariel chose to believe that the Master of Caliban was holding them in reserve for a swift, decisive blow against the insurgents.

The only other possibility was that Luther wasn't certain of his own allegiances, which was simply too terrible to contemplate.

'The situation is absolutely intolerable.' Magos Administratum Talia Bosk's metal-capped fingers sliced through the air in a gesture of Imperial pique. She sat perched on the edge of the tall, throne-like chair in the Grand Master's chambers, her slight figure nearly swallowed by the bulk of her layered robes. 'Our production quotas have slipped by sixty-three per cent at this point. Something must be done about these attacks at once, or we won't be able to meet our commitments to the Emperor's Crusade.' From the dread in Bosk's voice she might have been describing the end of life as she knew it - which, from her perspective, was probably close to the truth.

Bosk and most of her staff were from Terra, having been assigned to Caliban by the Administratum to oversee the planet's growing bureaucracy and its breakneck industrialization programme. Gleaming, metal-sheathed cables ran from recessed data ports at the base of her skull and wound about her bird-like neck before disappearing beneath the wide collar of her robes. Her shaven head was adorned with tattoos etched in holographic ink, drawing on her own bioelectric field to project shimmering images of the Imperial Aquila a few millimetres above her skin. The haptic interfaces covering the tips of her fingers were ornamented with tiny jewels and delicate whorls, like fingerprints, etched into their platinum surface. Her augmetic eyes gleamed with a cold, blue light as she regarded Luther across the massive oaken desk.

It was late afternoon, and the slanting light was creeping across the chamber floor from the tall windows on the west side of the room. The chamber, which normally seemed spacious to Zahariel, was crowded with regimental officers, staff aides and Bosk's fretful retinue of bureaucrats. He stood patiently by the window, his broad shoulders outlined by the setting sun, a data-slate gripped loosely in his hand. The meeting, intended to provide Luther with a status report from the planet's senior Imperial officials, wasn't going well.

Luther sat back in the Grand Master's enormous chair. Built for Lion El'Jonson's massive physique, it made the great knight seem almost childlike in comparison. He rested his elbows on the chair's broad arms and regarded Bosk coolly.

'Rest assured, Magos Bosk, there's no one on this planet more conscious of our obligations to the Legion than I,' Luther replied. Only someone who knew him well could detect the undercurrent of tension in his voice. 'General Morten, perhaps you could enlighten us on the current security situation.'

General Morten, outfitted in the dark green uniform of the Caliban Jaegers, cleared his throat and rose slowly from his chair. Like Bosk, he was a Terran, a decorated soldier of many years' service who had been tasked with creating the planet's defence forces. He was a short, stout man, with sagging jowls and a nose that had been broken so many times it was little more than a misshapen bulb in the centre of his weathered face. His voice was a steely rasp, thanks to a year fighting amid the toxic ash plumes of Cambion Prime.

'Caliban's major arcologies remain under martial law, with mandatory curfews in effect,' the general began. 'The riots appear to have run their course, at least for the moment, but we're still seeing isolated rebel attacks on checkpoints, precinct houses and infrastructure targets like water pumps and power substations.' He sighed. 'A heavy troop presence in the arcologies has sharply reduced the number of attacks, but it can't eliminate them completely.'