Now the room was almost empty, Sindermann could see that a body lay beside the pool. It was the body of a Luna Wolf, limp and dead, his helm off, his white armour mottled with blood. His arms had been lashed to his trunk with climbing cable.

'I don't...' Sindermann began. 'I don't understand, captain. I was told there had been no losses.’

Loken nodded slowly. That's what we're going to say. That will be the official line. The Tenth took this fortress in a clean strike, with no losses, and that's true enough. None of the insurgents scored any kills. Not even a wounding. We took a thousand of them to their deaths.’

'But this man...?'

Loken looked at Sindermann. His face was troubled, more troubled than the iterator had ever seen before. 'What is it, Garviel?' he asked.

'Something has happened.’ Loken said. 'Something so... so unthinkable that I...'

He paused, and looked at Jubal's bound corpse. 'I have to make a report, but I don't know what to say. I have no frame of reference. I'm glad you are here, Kyril, you of all people. You have steered me well over the years.’

'I like to think that...'

'I need your counsel now.'

Sindermann stepped forward and placed his hand on the giant warrior's arm. 'You may trust me with any matter, Garviel. I'm here to serve.’

Loken looked down at him. This is confidential. Utterly confidential.’

'I understand.’

There have been deaths today. Six brothers of Brake-spur squad, including Udon. Another barely clinging to life. And Hellebore... Hellebore has vanished, and I fear they are dead too.’

This can't be. The insurgents couldn't have-'

They did nothing. This is Xavyer Jubal.’ Loken said, pointing towards the body on the floor. 'He killed the men.’ he said simply.

Sindermann rocked back as if slapped. He blinked. 'He what? I'm sorry, Garviel, I thought for a moment you said he-'

'He killed the men. Jubal killed the men. He took his bolter and his fists and he killed six of Brakespur right in front of my eyes, and he would have killed me too, if I hadn't run him through.’

Sindermann felt his legs tremble. He found a nearby rock and sat down abrupdy. Terra.’ he gasped.

Terror is right. Astartes do not fight Astartes. Astartes do not kill their own. It is against all the rales of nature and man. It is counter to the very gene-code the Emperor fused into us when he wrought us.’

There must be some mistake.’ Sindermann said.

'No mistake. I saw him do it. He was a madman. He was possessed.’

"What? Steady, now. You look to old terms, Garviel. Possession is a spiritualist word that-'

'He was possessed. He claimed he was Samus.’

'Oh.’

You've heard the name, then?'

'I've heard the whisper. That was just enemy propaganda, wasn't it? We were told to dismiss it as scare tactics.’

Loken touched the bruises on his face, feeling the ache of them. 'So I thought. Iterator, I'm going to ask you this once. Are spirits real?'

'No, sir. Absolutely not.’

'So we are taught and thus we are liberated, but could they exist? This world is lousy with superstition and temple-fanes. Could they exist here?'

'No.’ Sindermann replied more firmly. There are no spirits, no daemons, no ghosts in the dark edges of the cosmos. Truth has shown us this.’

'I've studied the archive, Kyril.’ Loken replied. 'Samus was the name the people of this world gave to their archfiend. He was imprisoned in these mountains, so their legends say.’

'Legends, Garviel. Only legends. Myths. We have learned much during our time amongst the stars, and the most pertinent of those things is that there is always a rational explanation, even for the most mysterious events.’

'An Astartes draws his weapon and kills his own, whilst claiming to be a daemon from hell? Rationalise that, sir.’

Sinderman rose. 'Calm yourself, Garviel, and I will.’

Loken didn't reply. Sindermann walked over to Jubai's body and stared at it. Jubai's open, staring eyes were rolled back in his skull and utterly bloodshot. The flesh of his face was drawn and shrivelled, as if he had aged ten thousand years. Strange patterns, like clusters of blemishes or moles, were visible on the painfully stretched skin.

These marks.’ said Sindermann. These vile signs of wasting. Could they be the traces of disease or infection?'

'What?' Loken asked.

'A virus, perhaps? A reaction to toxicity? A plague?'

Astartes are resistant.’ Loken said.

To most things, but not to everything. I think this could be some contagion. Something so virulent that it destroyed Jubal's mind along with his body. Plagues can drive men insane, and corrupt their flesh.'

Then why only him?' asked Loken.

Sindermann shrugged. 'Perhaps some tiny flaw in his gene-code?'

'But he behaved as if possessed,' Loken said, repeating the word with brutal emphasis.

We've all been exposed to the enemy's propaganda. If Jubal's mind was deranged by fever, he might simply have been repeating the words he'd heard.’

Loken thought for a moment. You speak a lot of sense, Kyril.’ he said.

'Always.’

'A plague.’ Loken nodded. 'It's a sound explanation.’

You've suffered a ttagedy today, Garviel, but spirits and daemons played no part in it. Now get to work. You need to lock down this area in quarantine and get a medicae taskforce here. There may yet be further outbreaks. Non-Astartes, such as myself, might be less resistant, and poor Jubal's corpse may yet be a vector for disease.’

Sindermann looked back down at the body. 'Great Terra.’ he said. 'He has been so ravaged. I weep to see this waste.’

With a creak of dried sinew, Jubal raised his head and stared up at Sindermann with blood-red eyes.

'Look out.’ he wheezed.

EUPHRATI KEELER HAD stopped taking picts. She stowed away her picter. The things they were seeing in the narrow tunnels of the fortress went beyond all decency to record. She had never imagined that human forms could be dismantled so grievously, so totally. The stench of blood in the close, cold air made her gag, despite her rebreather.

'I want to go back now.’ Van Krasten said. He was shaking and upset. There is no music here. I am sick to my stomach.’

Euphrati was inclined to agree.

'No.’ said Borodin Flora in a muffled, steely voice. We must see it all. We are chosen remembrancers. This is our duty.’

Euphrati was quite sure Flora was making an effort not to throw up, but she warmed to the sentiment. This was their duty. This was the very reason they had been summoned. To record and commemorate the Crusade of Man. Whatever it looked like.

She tugged her picter back out of its carry-bag and took a few, tentative shots. Not of the dead, for that would be indecent, but of the blood on the walls, the smoke fuming in the wind along the narrow tunnels, the piles of scattered, spent shell cases littering the black-flecked ground.

Teams of army troopers moved past them, lugging bodies away for disposal. Some looked at the three of them curiously.

Are you lost?' one asked.

'Not at all. We're allowed to be here.’ Flora said.

Why would you want to be?' the man wondered.

Euphrati took a series of long shots of troopers, almost in silhouette, gathering up body parts at a tunnel junction. It chilled her to see it, and she hoped her picts would have the same effect on her audience.

'I want to go back.’ Van Krasten said again.

'Don't stray, or you'll get lost.’ Euphrati warned.

'I think I might be sick,' Van Krasten admitted.

He was about to retch when a shrill, harrowing scream echoed down the tunnels.

What the hell was that?' Euphrati whispered.

JUBAL ROSE. THE ropes binding him sheared and split, releasing his arms. He screamed, and then screamed again. His frantic wails soared and echoed around the chamber.