'Oh dear,' said the Doctor, his voice barely carrying above the animal cries from the corridor. His face was gaunt in the harsh neon light. 'The Mecrim know we're here.'

Seventeen.

A small number of the ape-like Rocarbies could hold back their frustration no longer. Enraged, they rushed at Defrabax, knocking him to the floor. They began to pummel his head and chest with their fists.

Jamie ran forward to help, but was pushed aside. The ma.s.sed Rocarbies were beginning to scream and shake their heads in delight.

An unexpected voice from the direction of the stairs cut through even the hollering of the apes. 'Stop!' The Rocarbies turned to see three of the moth-creatures stepping on to the concrete expanse, their wings unfolded, their hands outstretched. Jamie noticed that the head of one of the creatures was armoured, terminating in huge jaws like a man-trap. Perhaps this was one of the soldiers that the Dugraq had mentioned.

'Stop,' said the leading Taculbain again. 'This is not the way forward.'

The Rocarbies threw themselves to the ground and averted their gaze. 'It is the G.o.ds-among-us,' whispered one.

'They have a message for us.'

The Taculbain stepped through the crowd, brushing past Jamie, the Dugraq and the semi-conscious Defrabax. They came to a halt before the Rocarby leader, who risked a quick upward glance. 'Do not punish us,' he said. 'We have never heard your words before. We will do anything that you want.'

'We have been sent by our Queen,' said the Taculbain.

'We need your help. There is an enemy, a race of destroyers, that will soon move across our world. These creatures will kill all our peoples. Only if we unite will we stand a chance.'

'Of course,' said the Rocarby. 'What we have is yours. But this human . . .'

'For the moment he is of no consequence. Such matters can wait. These are the orders of our Queen.' The Taculbain turned to address the little Dugraq, who bowed respectfully.

'Your plan was to warn your people also?'

The scout nodded. 'That is correct.'

'Then we are of one mind. We will leave the soldier here to help organize defences against the Mecrim. We will accompany you.'

'Your help would be gratefully received,' said the Dugraq.

'And the man?'

'Oh, I think he'll survive,' said the scout, bending down to examine Defrabax's wounds. The mage smiled at the little creature weakly.

'Then let us go,' said the Taculbain. 'There is only small time before the beasts attack us.'

The Doctor, Zoe and the twins ran across the room to the only door that they could see. It hissed open with little prompting, revealing a small square chamber full of filing cabinets.

'Any ideas?' asked Zoe as they heard the creature smash its way into the cryogenic control room.

'Yes,' said the Doctor. 'We need a stronger door.'

'There's a weapons-testing room on this level,' she said, remembering with perfect clarity the map she had seen.

'Splendid,' said the Doctor, opening the only other door in the room.

As they ran into a short corridor the walls began to shake as filing cabinets were hurled aside in the small room. They didn't have much time. Zoe led the way down the pa.s.sageways. The twins brought up the rear, occasionally looking back at their pursuer. It had emerged from the room and was beginning to gain ground, although it was not yet running at full speed. 'I'd forgotten how ugly it was,'

muttered Reisaz.

They came to a halt before a huge studded door of dull grey alloy. Zoe pa.s.sed a hand hopefully over the sensor but wasn't surprised when it didn't open. 'I'll need a high-level clearance,' she said, setting to work.

'Do hurry, Zoe,' said the Doctor. The creature turned the corner, grunting with delight.

'Trust me, Doctor,' said the young woman. 'Computers always recognize a kindred spirit. Isn't that what you said the other day?'

'Just get the door open, there's a good girl.' The Doctor began to mop his brow with a large handkerchief. 'You can remind me of my less sensitive aphorisms at some other time.'

The doors hissed open, and they ran through. A hinged arm flicked into the s.p.a.ce between the closing doors and they began to slide open again. The creature impatiently pushed its bulk into the gap.

'Manual override!' shouted the Doctor, but Zoe was already at work. With a sigh of pneumatics the doors trapped the creature's shoulder. Zoe boosted the door's power intake to maximum, but the machinery groaned and was unable to fully close the doors.

With a roar the creature began to insinuate itself into the gap.

'Very well,' said Zoe quietly, mere inches from the snapping claw as she bent down to the emergency control panel once more. 'Let's try this.' She pressed a few controls.

A huge metal shutter began to grind inexorably down from the roof, moving into position just in front of the doorway.

'It's not going to close in time!' exclaimed Raitak, transfixed by the scene.

The creature seemed to be aware of the descending shutter and began to push downwards and into the outer door, its arm resting on the ground. Its head turned in their direction as it began to pull itself through the metal doorway.

With a sudden squeal the shutter ground through the creature's arm and touched the floor. The severed claw flexed for a moment and then stopped. The machinery was silent.

'Well done, Zoe,' said the Doctor.

'How long will that keep the creature out?' asked Raitak.

'Just long enough for us to think of something,' said the Doctor, turning to examine the room for the first time. The shutter began to vibrate as the Mecrim slammed into it in frustration.

Half of the room was dominated by computer and testing equipment, the other was a glorified firing range. A selection of weapons and ammunition was locked in cases along the walls. The Doctor inspected the armoury slowly.

'Crude,' he muttered to himself. 'Not what we're looking for anyway.' He turned to Zoe, already seated at a console.

'Find out everything you can about the Mecrim,' he said.

Within minutes the screen was filling with information.

'Some of the files are corrupted,' she announced. 'But there seems to be a complete backup copy linked to a personal directory. I'll skim through that.'

'Switch it on to audio,' said the Doctor, sitting cross-legged in the centre of the room. 'Let's hear what happened to these people.'

The synthesized voice that filled the room was a computerized memory from the dawn of time. '- isn't good enough stop I don't believe that we can wait that long stop Nikolas has done some more tests semicolon appended to this memo stop I'm sure that you now appreciate the nature of the problem that we face stop Two dead already stop new paragraph I request immediate evacuation stop end read back and send when ready.'

Kaquaan stood watching Defrabax's house, recent events fresh in her mind. She had slipped quietly through the city streets, desperate to remember the location of the old magician's house. As she had turned the corner she had seen a tall figure walking imperiously towards Defrabax's abode.

She had crept into the shadows and had watched as the red-robed knight pushed open an unlocked door and walked inside.

So, Zaitabor had returned to the surface. Why? The unlocked door suggested that Cosmae was not alone inside.

What did Zaitabor and his minion want with the boy?

Kaquaan had moved into a better position, watching the front door. She knew that there must be an entrance around the rear of Defrabax's house - she remembered her first encounter with the homunculus - but Zaitabor's a.s.sured manner seemed to indicate little interest in concealing his movements.

She emerged from her reverie, aware only of the slow pa.s.sing of time. Her mind invented and refined countless scenarios, the most likely of which seemed to be that the knights had murdered Cosmae and departed through the back door. Only when she was about to run to the front to investigate was there some movement from within.

Zaitabor and Araboam emerged, both still wearing the robes of the brotherhood. Cosmae stood between them, his face bruised, his hands bound behind his back. A sword to his throat ensured silence.

Kaquaan took another step back into the shadows. She nudged into something that she knew wasn't a wall. A hand closed over her mouth.

The Doctor ran the words of the message over in his mind. With a chill of impossible remembrance he realized that he recognized the woman's voice from his waking deam. 'Who was that speaking?' he asked.

Zoe paused the playback. It's Dr Jenn Alforge, head scientist on Project Mecrim. A memo to a Ciaran Dugied at -'

'Play the whole file,' said the Doctor, staring at the marks that were beginning to appear on the metal shutter. 'I think we've got time.'

Zoe tapped some commands into the console and then the voice started again.

'Computer-based syntax, punctuation, paragraph breaks.

Confidential letter from user to Dugied, insert date and time.

'Dear Ciaran,

'I'm finally settling in. Good staff here, reasonable surroundings. Less than happy about the Mecrim project itself, but then, you already know that. Nik's preliminary report appended to this.

'Is the dog still quarantined? It's a shame, I think - even though you know the good reasons behind it.

'Heard of some border skirmishes the other day - not reported on the civilian news, quelle surprise. You won't forget us, will you?

'Best wishes, Jenn.'

The voice changed from the woman's to that of the computer's own clipped sounds as it worked its way through the report.

'Genetically adjusted Mecrim creature, provisional cla.s.sification. Order: Reptiloprimate. Family: Astridae.

Genus and species: Singropoda mecrimus. DNA owned and licensed by the Butler Inst.i.tute.

'Height: 1.6 metres to shoulder. Weight: up to 150 kilograms. s.e.xual maturity: two to five years. Mating season: late spring to summer. Gestation: six months.

Number of young: one to two. External gender differentiation: none. Habit: Social, lives in large groups.

Diet: large mammals or equivalents, occasional carrion, sometimes supplemented by berries and bark. Lifespan: estimated to be over 20 years.

'Appearance and other factors: The Mecrim is a six-limbed bipedal humanoid. It has an internal skeleton, complete with humanoid rib-cage protecting vital organs, but its legs and primitive arms resemble those of an insect, featuring vestigial exoskeletal structures and secondary jointing. With the exception of its armoured head a Mecrim gives the appearance of having no skin, with the muscle and ligaments exposed. In actual fact, the top layer of Mecrim muscle performs this function, being incredibly tough "skin subst.i.tute".

'A Mecrim has four toes of equal length, arranged at right-angles in the shape of a cross. Its legs feature an upper knee and an extended "ankle" that functions as a secondary joint. The musculature seems to allow for a reasonable turn of speed, although by temperament and even when hunting the Mecrim could be described as being casually arrogant.

'The upper limbs consist of a pair of arms that terminate in a four-digit "hand" and a pair that feature a more primitive hooked claw. The head incorporates a complicated mouth and the eyes are partly concealed. Tests reveal that Mecrim see heat rather than light.'

Zoe paused the playback and beamed. 'So I was right!'

The Doctor nodded. 'You were. But what can we do with that piece of information?' He rose to his feet, glancing across at the shutter. Huge dents were appearing in it now.

'You said that the creature was always attracted to the largest possible "heat signature"?'

'Yes,' said Zoe. 'I speculated that this was because it would equate that with the most likely threat to its own survival.'

The Doctor nodded. 'And presumably any one Mecrim can recognize the pattern of one of its own kind and therefore not attack.'