They were lost. Tahlia knew it was Grifford's fault, but decided to hold any recriminations back. They did not have the time for an argument.

Her brother had been running fast, trying to follow Vlambra's bloody trail back the way they had come, but somehow he had left a ladder on the wrong level and the trail had ended. They should have turned back to find it, and Tahlia suggested as much, but Grifford would not listen. He had gone on, jumping recklessly down steps and clambering up ladders, heading for the centre of the chamber where the tower stood. He disappeared around a corner, and she heard him curse. Rounding the corner close behind him, she skidded to a stop when she saw the walkway ahead blocked by a tangle of pipework, and a bank of valves and gauges.

"This is your fault!" her brother growled.

"My fault!"

"We should have stayed with Kralmir!" Grifford began to clamber over the pipes to see what was beyond.

"I forgot about the nadidge," admitted Tahlia. "But so did you! How was I supposed to know that..?"

"Shut up!" snapped Grifford. He was kneeling on top of the pipes, peering down into the darkness. "There!" he said, pointing.

"What?" asked Tahlia, and began to climb up the pipes behind him, but before she could reach him he had thrown his leg over their far side and disappeared from view. She heard a distant clang somewhere below, and when she reached the top of the pipes and looked down she saw a narrow walkway some two metres below. It was shaking as her brother sped away along it. On one of its handrails, still gleaming wetly in the blue light, was one of Vlambra's bloody handprints.

* * * * *

Dak's eyes sprang open with Kralmir's scream. She did not know if they had been closed for seconds or hours, but consciousness returned swiftly at the sound of his cry. A cry that pierced, then dwindled as her friend's baby brother disappeared upwards.

"No!" she cried, and reached up after him, into the tangle of pipes.

She did not touch him, but her fingers found the cold clamminess of the sinuous tail that had curled about him and hauled him up out of his hiding place. If she had touched such a thing a few short hours before, she would have released it, screaming with its vileness, but she had seen, heard and felt much worse things that morning, so instead she tightened her grip.

The creature hidden somewhere in the darkness above her hissed, and she heard the snick of its blades extending, a short second before pain lanced her arm. Her instincts gave her no choice but to let go, and Kralmir was gone.

She clutched at her arm, feeling the dampness of her own blood against her palm.

"Yeltov smelt you down!" she hissed.

She could hear Kralmir's receding screams, and the scuttling of the nadidge as it clambered away through the pipes, its silent stealth done with, replaced by a need for swiftness.

Dak slid from beneath the pipes, feeling as though someone else were moving her. She could not feel her foot, and her arm was a singing pain, but somehow she pulled herself out. The nadidge leapt across the room above her, Kralmir wrapped tightly behind it, and it swung from pipe to pipe towards the open door.

"Oh no, no, no!" she sobbed, but a part of her was thinking differently.

'Let it go. The child is not your concern. This is not Engineer business. Let it go and you will be safe.'

With a jump, the nadidge landed on the floor and leapt towards the doorway.

'Look after him,' Grifford had said. He had commanded it. 'You are an Engineer. You should not be taking orders from those of the fortress.'

And maybe if it had been anyone else who had done the ordering...

Dak pulled herself off the floor and hauled herself up towards the one valve amongst the tangle of pipework above her whose purpose she had understood. The plaque bolted above the large red wheel valve had a single word stamped on it. Doors.

Her second step brought her weight down on the leg that had no feeling, and she stumbled. In her fall she caught hold of the wheel and grasped it with both hands, put all her weight against it, and heaved. The valve was as well maintained as the rest, and it turned easily with her strength, the unnecessary force she had exerted on it sending her crashing to the floor. She heard the pipes above her hiss, and felt two great grinding booms through the floor, followed by a high pitched screech of pain.

One hand still clutching the wheel, she looked up to see that a great slab of metal had slammed down to cover the doorway leading down into the tower. Another slab covered the door that led outwards, and the nadidge was curled up at its foot, its squeals of agony drowning out Kralmir's own cries. One of its arms was caught, crushed beneath the door. The assassin was trapped.

Dak gave a great sigh. She had done it! It could not get out.

'Yes, but also, no one else can be getting in.'

She let go of the wheel and turned herself to sit on the floor.

The movement must have alerted the creature, because it turned its head over its shoulder to regard her.

Its mewls of agony stopped, and it gave an angry hiss.

Dak had no energy left, and she felt like she would not be able to move, even if she were capable of thinking of something that she could have been doing. She would wait for Tahlia to get back. Her friend always had an answer. She looked around the room, but her head felt unsteady and her eyes impossibly heavy. She closed them tightly, in the hope that when she opened them again they would be focussed.

Kralmir had stopped screaming, and in the room's silence she suddenly heard two snicks of sound.

Her eyes had gained enough focus to see that the nadidge had carefully placed Kralmir on the floor, close to where his nursemaid lay dead, and now he was lying beside her, equally still and silent. The nadidge still watched her with its six red eyes, its twin blades extended from between the knuckles of its free arms.

'Those cannot harm me now.'

The nadidge's twin mandibles clicked shut as she watched it, and then it turned its head away from her, giving its attention to its shattered arm.

'It is trapped,' she said to herself. 'It cannot be getting to me. It cannot.'

But then she watched in silent horror as the beast got to work on itself with its blades.

* * * * *

Tahlia caught up with Grifford as he threw himself down the spiral stair from which Vlambra had dropped their brother only a short time before. His feet hit the platform above the broiling waste reservoir, and he was halfway across it and heading for the doorway into the tower when a deep resonating boom rumbled out of it. Grifford did not pause, and flew down the steps and into the darkness. Tahlia followed, leaping down the steps three at a time. She heard Grifford's curse a scant few seconds before she rounded the stair's final turn and collided with him where he knelt on the floor. His head was bowed and resting against the heavy slab of metal that blocked the doorway ahead.

* * * * *

The morning had been horror piled upon horror for Dak, so much so that her brain had been numbed by it, and the sight of the nadidge slicing away its maimed arm did little to pierce the protective wall encasing her thoughts. She watched the creature as though in study, as it sliced through its own skin.

She had yet to begin her formal lessons in the mechanics of living beings, but her father had plenty of books on the matter, mostly consisting of illustrations. He also had quarter scale models of both a human and a madriel skeleton hidden away behind a curtain at the back of his workshop because, he maintained, if you were making armour designed to protect a thing, then it was worth the while understanding the thing it would be protecting.

She knew how razor sharp the nadidge's blades were, and saw that they had little difficulty in the task of cutting through its skin, and then through the sinews and muscles beneath, but the task was still taking time.

'It will be having trouble with the bone,' she thought. A slim blade like that would not cut through bone. It would be looking for where the bone is broken and be cutting through the flesh there.

As she watched it work in fearful fascination, the logic of her assumption almost made her laugh, and that brought her back to herself. She knew she should be doing something else besides watching. Soon the creature would be finished with itself, then it would turn its attention back to her. She cast her eyes about the room, looking for something that could save her. They passed over the stand of heavy valve leavers, and the rack of long pressure hoses, until they alighted on the table with its two heavy chairs and the signalling device on the wall above.

She tried to stand, but her leg would no longer move, so she began to drag herself across the floor, leaving bloody hand prints behind her. The distance was not far, but it seemed to take an age, and only when she reached the table and heaved herself into one of the chairs, pushing with the leg that still retained feeling, did she look back to where the creature was trapped.

Where it had been trapped, because it was not there.

The only evidence of it was a pool of its dark black blood around the base of the door, with the tatters of its arm poking from beneath it.

Her eyes darted about the room, but there was no sign of it. There was no sound but the pounding of her heart in her ears, and when that slowed there was only silence.

The creature must have gone. There must be another way out of the room; a vent somewhere behind the pipes, or a drain in the floor.

She reached out a shaking hand towards the signalling device. She watched as her hand turned the small wheel that would make the device active and call for attention at its counterpart machine, just as she had learnt in her signalling class.

The smallest of sounds broke the quiet as something small landed on the table in front of her, breaking apart and splashing dark bloody beads across its wooden surface. More drops fell, pattering the table, and her hand.

She screamed.

The nadidge landed in front of her, grasping her wrist in its hard talon. Without thinking, she pushed away from the evil thing, and the chair toppled backwards, colliding with the stand of valve leavers before tumbling sideways and spilling her onto the floor. The levers fell about her, clattering and clanking on the metal floor. They struck her shoulders and chest, but none hit the creature she had pulled down to the floor with her, its claw still clamped about her wrist. It squatted on her stomach, and when the echoes of the falling levers had died, it fixed its six red eyes on her, and hissed.

Dark blood had started to scab on the stump where it had severed its own arm, but it still fell in sluggish drips onto her filthy tunic.

"Please!" she begged. "I do not want hurting."

Its eyes did not leave her, but it extended one arm and pointed across the room, at the red wheel that she had turned to close off the doors. Its mandibles twitched, and it clicked and crackled something at her. The wheel had not moved, but on the floor beneath it were black drops of blood.

By Yeltov it could move quickly!

It had speed, that was for certain.

But not strength.

It needed her.

"I will not," she said, sounding in her ears more confident then she felt. "You cannot be making me open that."

Its blades snicked out again. One pointed still at the bright red wheel, the other one the creature lifted to her face, and she felt the needle sharpness of it as it came to rest on her cheek. She bent her head back as far as it would go until it touched the wall behind her.

She did not have a pretty face, that much she knew, but she still did not want it lacerating.

Her eyes flicked around, and she saw something above her that gave her hope for her deliverance, but she was too scared to move with the blade pressed to her cheek.

"Please!" she said.

The blade went from her face, and she almost sighed with relief. She pulled back, shifting her weight where it rested uncomfortably on her elbows, and she felt something cold beneath her hand. She wrapped her fingers around the heavy bar of the lever. Maybe she could...

The blade was pushed forward once more, pricking at the soft flesh within the socket of her left eye.

She froze.

'Not my eyes! It cannot be wanting to take my eyes!'

The creature gave a malevolent hiss, as though reading her thoughts.

It lowered its elbow, so the blade angled upwards towards the softness of her eye. She saw the muscles in its fist tighten, its fingers bunching around the root of the blade jutting from between them. Maybe it would take one eye to give her a lesson. After all, he only needed one eye to turn a wheel. In fact, she did not even need one.

She heard a shriek, and for a portion of a second wondered why she screamed before she had even felt the sharpness of the pain. Then she saw the creature pull back, its blades slicing around to defend itself, because it was not her that had screamed. The high noise had come from the whistle on the signalling machine above the table as it called for attention. The noise stopped, and the nadidge hissed in aggravated frustration, but then the whistle came again and the creature flinched at the sound, hissing at the machine in challenge. Its attention only returned to Dak when it caught the hint of movement from her.

She pushed herself up, one arm supporting her weight, the other raised above her head, the heavy lever bar clutched in one blood caked hand. The creature whipped its blades back around, striking at her fast and leaving another bloody cut on her arm.

She screamed.

It was not a scream of pain, but one of exertion as she put all her strength into turning the valve above her head that she had pushed the lever into. It was an old ring-valve; its operator nothing more than a heavy loop of metal. Any lever bar could be fixed into it and turned. The lever she held was not made for it, but that did not matter. It fitted, she pulled, and the valve opened.

It had a disconnected port, and to open such a valve without a regulator hose attached was a foolish thing to do. Not to mention dangerous, particularly for anything standing directly in front of it.

There was a furious hiss, and a burst of violent vapour struck the nadidge, enveloping it in an icy white cloud. The screech that burst from the creature drowned out the sounds of the hissing valve, Dak's cry, and the third whistling note of the signalling machine. One of the nadidge's blades sliced the air in front of her, but then it was falling backwards, still screeching as its talons clawed at its own face and body, which had been turned a sick white colour by whatever substance had burst from the pipe.

Dak could not imagine what the pipe above her contained, but some droplets, thrown by the spitting valve, landed on her, and she felt them like burning ice, eating at her skin. She fell to the floor, rolled over, and pulled herself away, feeling more drops fall on the back of her legs, and only when she was well away from the valve's hissing did she turn herself over to see what had become of the nadidge.

It was curled on the floor a few metres away, mewling and scratching at its pale skin where it had been frozen white. Ugly welts and blisters covered it, and where the creature's claws had caught them they had been torn open, and they were leaking a thin clear fluid.

Dak pulled in a shocked breath, and the creature must have heard because its head flicked towards her. She bit off a scream at the sight of its face for it, like the rest of the creature's body where it had been touched by the cold vapour, was ice white and blistered. Its eyes, once red malevolent globes, were destroyed. Nothing remained of them but six empty sockets, rimmed with frozen crystals. It opened its mandibles wide, and she saw the frozen flesh about them crack, and the blisters there split open to leak more clear liquid, which froze as it touched the skin of its face.

"Oh why will you not die!" she moaned, and the creature uncurled itself.

Its movements were slow, but once it had gained its feet it came on faster. Its lower body and legs were untouched by the deathly liquid, the skin there still shadow black, as was the skin of its lower arms and its hands. Its third remaining hand was frozen into a claw. It stalked forward, upright but crouched, and as it came its deadly blades snicked out from between its fingers once more.