The cryogenic chamber had been almost completely destroyed. The individual units had been smashed and overturned, the door breached as if it had been tissue paper.

The Doctor sighed. 'I wasn't too keen on my original plan,'

he remarked. 'And now we'll never know.' He tapped the gun. 'Come on.'

'Where are we going?' asked Zoe.

'The domain of the Dugraqs is nearby.' The Doctor walked down the corridor, Zoe and the twins following close behind. 'Hopefully Jamie and the others will be there by now. The problem is, I expect the Mecrim will be as well.'

'Doctor,' said Zoe as they walked, 'those files we looked at. That gut microbe that almost wiped out the entire colony.'

'Yes?'

'With Mecrim on the loose, surely the plague will recur?'

'Well, the ancestors of Defrabax and the others probably still carry the immunity to the disease.'

'But I don't, and neither does Jamie.'

'I know,' said the Doctor. 'But let's deal with the Mecrim first, shall we?'

A Dugraq walked around distributing ammunition as calmly as was possible under the circ.u.mstances. Jamie took a few steps back, glancing over at the scout to see how he was reloading the gun. They avoided eye contact, for both knew that the Dugraqs were being ma.s.sacred.

As Jamie pushed the bullets into the chambers he totted up the carnage. As far as he was aware getting on for fifty Dugraqs had been killed. Over ten Taculbain had died trying to defend them. Only two Mecrim had been injured, in both cases the result of gunfire being trained on a wound opened up by a Taculbain soldier. Although moving a little more slowly than the others, neither Mecrim seemed unduly hindered.

There were over ten Mecrim now. They trotted forwards, and the Dugraqs fanned away. Jamie heaved a sigh of relief as another group of Taculbain soldiers took position in the air just above the Mecrim.

This couldn't go on much longer.

Cosmae watched Zaitabor sit in front of one of the many box-like constructions. Each was covered with changing lights that formed patterns and words. The knight arranged all the papers in front of him. Then he began pressing nodules on the device in front of the box.

All the boxes showed different pictures. There was a groaning hum from somewhere, like the earth moving. The noise began to rise in pitch. The boxes let out more and more red light.

'My lord,' said Araboam. 'How know you so much about this infernal building?'

'The Higher is most gracious!' cried Zaitabor. 'Have you no faith?'

At that Araboam lapsed into worried silence.

Cosmae watched the red lines on the metal cubes get longer and longer.

Jamie heard a sad voice at his shoulder. 'h.e.l.lo, Jamie.

You seem to be a natural marksman.'

Jamie turned, managing a smile in spite of the stench of death. 'I've never picked up one of these things before.'

'Try this,' said the Doctor, offering Jamie the weapon that he had carried with him. 'Fire once at every Mecrim that you can. I think most of them are here now.'

Another flight of Taculbain had been killed. The Mecrim - Jamie lost count how many there were - began to stalk forwards again.

Jamie had seen Redcoats carrying rifles and felt a little more comfortable with the weapon the Doctor had given him. He placed the stock into his shoulder, and closed his left eye. A few moments later he squeezed the trigger.

Nothing happened. The least Jamie was expecting was a small explosion like that which destroyed the Furnace.

'I was sure I hit it!' he exclaimed, turning to the Doctor.

'You did,' said the Doctor. 'Look!'

A couple of Mecrim were already attacking their companion, severing limbs like children picking legs off an insect.

'Now,' said the Doctor. 'Keep firing, one per creature.'

Jamie glanced over his shoulder as the Doctor moved back to where Zoe and the twins stood, arms around each other's shoulders, faces wet with tears.

Gritting his teeth, Jamie stared back at the Mecrim that stood in front of piles of corpses. He fired the gun again.

And again. And again.

The building was ablaze with light and rumbled with what sounded like thunder. 'A glorious sound!' exclaimed Zaitabor. 'The sound of destruction, the warning-note that will be heard by all who have meddled with science.'

'Stop!'

Cosmae turned towards the voice but was pulled harshly across the room to Zaitabor's side. A knife appeared at his throat. He was just able to turn his head to see the homunculus walking into the room. Araboam's mouth dropped open with surprise.

'Stop,' repeated the homunculus. 'Return all controls to their initial settings. If you bring all systems on-line then there will be a ma.s.sive explosion.'

Zaitabor laughed. 'There will? Good. I thought as much.'

'I have been ordered to stop you.'

'Really? That pesky Doctor fellow still trails my shadow.

And what will you do?'

'I shall use the minimum force necessary. But if you do not stop I shall use force.'

'Make me,' said Zaitabor, turning his back to the tall grey figure. The knight casually operated some controls.

Cosmae watched the homunculus walk across the room.

'Come any closer,' said Zaitabor, holding the knife to Cosmae's throat again, 'and I shall kill the boy.'

The homunculus stopped, confusion audible in its voice.

'The Doctor has ordered me not to endanger life.'

'Good,' said Zaitabor. 'Now that I have your cooperation, tell the Doctor that none of us will survive the retribution of the Higher!'

Cosmae stared at Araboam, hoping for some hint of rebellion, but his eyes were glazed.

'I shall contact the Doctor,' said the homunculus.

'I'm sorry you had to see more death and destruction,' said the Doctor.

'It's real, it happens,' said Zoe simply.

'Will it soon be over?' asked Raitak.

'I think not,' said the Doctor. 'We still have a most unusual madman on the loose.'

As if on cue there was a shrill noise from the Doctor's pocket. Defrabax sighed sadly but said nothing.

The Doctor rooted through his clothing for the communications device and switched it on. The picture cleared to show the android in the power station control room. The Doctor stared down at the little screen in the communications unit, watching Zaitabor who stood just behind the android.

'Doctor, I have failed,' reported the android. 'I have been unable to prevent the -'

'Move away, machine!' shouted Zaitabor, walking forwards, dragging Cosmae behind him and still holding a dagger to his neck. 'Greetings, Doctor.'

'h.e.l.lo, Zaitabor. At least, I a.s.sume that's you and not some clockwork toy.'

'No tricks now, Doctor. It is I, Zaitabor, humble instrument of the Higher.' The little figure on the comms unit stared defiantly upwards.

'Murderer of a civilization would be a more appropriate epitaph,' snapped the Doctor.

'I would not expect one so steeped in evil to understand the mysterious ways of the Higher.'

'I suppose nothingness is rather mysterious, in an empty sort of way,' said the Doctor. 'That's what you'll usher in if you operate all the power station's systems.'

'Indeed, Doctor. I find the prospect thrilling!'

'I wonder why,' said the Doctor. 'In fact, I have many questions to ask you. For example, why do you know so much about science? Few people could switch a nuclear power station back on, even if they were following Defrabax's instructions. And how did you create the clockwork version of yourself?'

'To defeat an enemy you must know your enemy.'

'Then perhaps you can answer this simple question. Who are you?'

'I am Zaitabor, acting Grand Knight, faithful follower of the ways of Kuabris and Rexulon.'

'Really? Then who are your parents?'

Zaitabor looked puzzled. 'I . . . I don't remember my parents.'

'Why?'

'I don't . . . I'm not sure.'

'For a man claiming to be tapped into a divine power, you don't know a great deal,' said the Doctor. 'Shall I tell you who you are?'

'No, I must destroy this -'

'Listen to me!' The Doctor's voice carried great conviction, even over the flickering comm link. 'Many, many years ago a Mecrim gut microbe was accidentally released into the atmosphere, resulting in a virtual plague.

Almost the entire civilization was wiped out. However, some humans survived, developed resistance to the disease, and over the centuries their descendants spread out over the entire world. It's not surprising that the city that formed over the top of the older, more advanced one would be so afraid of science. A deep fear of what had happened was pa.s.sed down from generation to generation. Whoever Kuabris and Rexulon were - if indeed they existed - they were certainly aware of the fear that technology engendered in them.'

'Your casual blasphemy will be -'

'But you, Zaitabor,' said the Doctor, his voice quelling even the knight's outrage. 'You are not one of those descendents.'

'Then who do you say that I am?'