The door opposite opened onto an equally dark space. Turning the tricorder about in her hands, Christine saw the light shine off walls that were close on either side.

'A corridor,' she murmured under her breath, and Spock nodded. 'You've been along here?' she intuited, and he inclined his head again. She saw tension in his jaw and neck muscles and knew that whatever he had been along here for had not been a pleasant experience.

'Do you have any idea which way to go?' she asked hopefully.

He shook his head. She scanned the surrounding area for life-signs, and found none. She glanced at Spock's shadowed form and then began to walk down the corridor, feeling as though she were leading a psychiatric patient between wards. She did not want to think of Spock in that way. She did not want to think that whatever had been done to him to leave him as this silent, introverted labyrinth might be permanent or long-term.

She ran through possible causes in her mind for this apparently selective mutism. It was obvious that he could talk. He had spoken those two words earlier – I fell. What had allowed him to say that much? Was it that the falling had been before, and all that was bad had happened afterwards? Or was it just a chance moment when he had felt able to speak? Perhaps there would be other such moments when he would allow her to hear his voice, hoarse and ruined as it was.

That hoarseness lingered in her mind. As if he had been screaming, she thought again. She shuddered to think what might make Spock scream. Whatever had happened it was almost certainly mental trauma. There was barely a sign of physical abuse apart from the results of neglect.

She turned towards the left as the corridor forked, and Spock's hand suddenly gripped her arm with surprising force. She stopped abruptly, peering into the darkness ahead.

'You've been down there?' she asked, turning the light on his face.

He nodded. He looked paler than ever. Then his lips worked as if he were fighting against a great impediment and after a moment he said, 'They are more…'

She stared, hoping she was successfully hiding her frustration.

'They are more?' she repeated. 'What? More likely to be down there?'

He inclined his head, and turned resolutely towards the right.

Looks like we're going right, then, she thought, but she kept her thoughts to herself. She was sure Spock would not appreciate the flippancy of the remark. She was almost certain, though, that it would take a herd of bull elephants to pull Spock down the left-hand corridor. She had rarely seen him afraid, but he was afraid of that.

They continued to walk, the tension prickling at Christine's back and legs as she moved. This place felt like a set from a horror film, a deserted and decaying facility that nevertheless had life – hostile life – lurking in the shadows.

She kept checking the tricorder for life signs as they moved. If there were people down here, and there must be some, they were either few, or infrequent visitors. Nothing appeared on the tricorder screen and the dirt and rubble grew thicker as they walked. She felt increasingly as if she were waiting for someone to leap out of the darkness and grab at her, no matter how unlikely that eventuality.

She had set the tricorder to scan for life, food, and water. They seemed to have been walking for hours through this dark maze and the thought of being forever trapped down here was starting to prise uneasily at her composure. The best way to ensure survival was to ensure a supply of food and drink, and after some time a spike on the screen showed a definite water source nearby. She sighed with relief and showed the screen to Spock. The water in her flask was growing low with two of them drinking it.

He looked towards a door to their left, and cautiously she pushed it open.

'Empty,' she murmured, checking and rechecking the tricorder for life signs.

She felt at the side of the doorway for the obligatory light switch, and found it – but this time no light flickered on. The increasing rubble in this area was obviously a sign of a greater neglect. She sighed and walked forward, holding the tricorder high and letting the meagre light shine into the air.

'I – think it might be a bathroom,' she said in a low voice as the light glinted off metallic objects nearby. 'You can see better than me in this light, I'm sure. What do you think?'

Spock stepped forward to join her, looking about himself with a guarded expression. He seemed to be waiting for something to happen, for the lights to snap on or for one of his anonymous captors to appear from the gloom.

He reached out tentatively towards one of the metallic objects and touched a small lever that Christine had not been able to see. Water gushed forth, and he started back.

Christine pointed the tricorder towards the water and scanned it.

'It's clean,' she said in a low voice. 'Drinkable.'

She opened her flask and held it under the flow until it was full again. Then she cleaned her hands and washed the dust and dirt from her face and swept water into her mouth with her cupped hands. Finally she straightened and looked at Spock. He was standing motionless, staring at her but making no move to join her at the basin.

'Mr Spock, are you going to drink?' she prompted him.

He took a step forward, but made no attempt to scoop water from the tap. She smiled encouragingly, and then took hold of his hand lightly about the wrist, moving it under the water. He started briefly but did not resist as she carefully washed some of the dirt from both his hands. It was hard in the faint blue light to tell what was clean and what was not, but she could feel the difference as his palms and fingers became softer, and slick with the feeling of water over clean skin.

She hesitated, looking down at his hands, resisting the urge to help clean off the rest of his body. In his state she did not want to risk him growing too cold. He was trembling already – not with cold, she knew, but with exhaustion or shock or whatever stress was assailing him.

'You need to sleep,' she said decisively.

He looked at her with an expression that almost certainly meant denial. She raised the tricorder and scanned him.

'You're malnourished, you haven't eaten anything since I found you, and you're suffering from – ' She faltered, at a loss as to how to describe his condition. ' – from some kind of undiagnosed trauma. Your brain is also showing signs of severe sleep deprivation. You need rest,' she said firmly.

Spock looked down at his shaking hands and then wordlessly held one out towards her pack. Her eyebrows raised in surprise. She got out a ration bar, carefully choosing one of her own rather than the sickly looking orange ones with which he had been supplied, and held it out to him. Slowly, as if he were consuming ashes, he ate it.

'You still need to rest,' she told him afterwards, holding out the flask of water to him.

The look he gave her then was briefly rebellious, but there was a greater aching tiredness that overwhelmed it and settled in his eyes, drawing him away from her again.

'For now, Mr Spock, I am your medical senior,' she said firmly. 'Sleep. That is an order. It's not logical to go on without rest. You're getting clumsy. We'll be found, and you'll end up right back where I found you.'

That seemed to reach him. There was a tightening of the muscles in his face, and he looked about the ruined bathroom warily despite the darkness being all-consuming.

'Stay there for a minute,' she said, and she began to make a careful investigation of the periphery of the room, looking for any other doors out of the place. There were none but the one by which they had entered. She discovered a number of metallic vents set very low to the floor which she speculated might be toilets, but other than those and the rank of basins there was nothing in the room.

'There's no other way in,' she assured Spock. 'Come on over here. I want to be near the door, in case – '

He moved over to the wall and bent, brushing away dirt fastidiously with the palm of his hand, and then settling on his side on the floor. Christine watched him closely as he closed his eyes, suspecting that he would feign sleep rather than fall into it. She opened up her medical kit and shone the light on the capsules inside before selecting a light sedative. It would be enough to kick him over into a natural sleep, but would not impede his ability to react if she needed to wake him.

His eyes flickered open as she touched the hypo to him.

'Just to help you sleep,' she said softly, depressing the trigger.

There was a moment of betrayed anger in his eyes and then they drifted closed again, and he slept.

Christine sat, watching him. She felt guilty at giving him the sedative without allowing him the option of refusing, but in her judgement he couldn't continue much longer with the levels of stress he was experiencing without collapse. At least now his heart rate was settling again and she could see the lines of tension disappearing from his body.

Finally she set the tricorder to alert her if it detected life signs and then closed the screen, leaving them in darkness. She could sit here gazing at the faint light reflecting from Spock's limbs for hours, but it made sense for her to get some rest too. She leant back against the wall, the tricorder held against her body, and closed her eyes.

Time drifted past, but she did not sleep. She listened. She listened to Spock's quiet, regular breathing, and to the odd creaking sounds that metal made when the temperature changed around it, and to the occasional scatter of debris falling to the floor. She listened for footsteps or speech, but she heard nothing of that kind.

It was merciful, perhaps. Merciful that this place was mostly deserted, that the beings who had so traumatised Spock were nowhere to be seen. But she found herself wishing, almost hoping, that someone would make themselves seen, even if just so she knew what she was hiding from. If they knew enemies were in one place, they could be sure to stay in another. This way she was waiting, always waiting, for the sudden appearance of an alien being.

She had no idea what these people looked like. She had no idea even if the people living down here were the original inhabitants of this planet, driven underground by their war, or perhaps others, come here by chance just as she and Spock had. She had seen plenty of beings from plenty of worlds and her mind conjured images as mundane as human-identical species and as alien as tentacled and boneless beings that moved by osmosis. Uncertainty was a terrible thing.

Spock stirred restlessly and she flipped open the tricorder, thanking the lord for the almost inexhaustible battery packs that these things had. She turned the bluish light onto his face and saw his eyes scrunched shut and his mouth twisted in a very un-Vulcan grimace. She reached out a hand to brush the hair from his forehead, allowing herself a gesture in his sleep that she would almost certainly have never made while he was conscious, and –

She was Spock, moving through a parched landscape, turning, turning, seeing only ruins that crackled with radioactive residue. Regret rippled up in him, and was pushed down again, pushed away.

So like humans, so like humans…

He was speaking through his communicator, a cord of desperation rising; crackling was the only response.

'So like humans, Captain. I require beam up. I am lost.'

He was lost. There was something behind him. There was something coming. He couldn't see it. Illogical to be scared. So much was not rational here. Dry, broken walls, the captain smiling at him placidly from somewhere obscure. No help, and something behind him, prickling at his back.

A figure stepping up to him, vaguely humanoid, Spock's height, its eyes sharp and too close, its eyes seeing him and not allowing him to turn away. Its body furred. Quite beautiful, like a jewel, catching the sun with a million strands of iridescent hair, patterned in red and leaf green and rich, royal purple. The iridescence blue and shimmering whenever it turned under the diamond sun.

That noise coming from somewhere, fluid and ornate and incomprehensible, like a song. Like a song that meant nothing and left him blank with confusion, coming from what some might call a mouth.

Naked. It was naked. He was clothed. Too close. Its eyes were close to him, its fingers prying at the looseness of his clothes, and he was lying now, naked. The ceiling was too low, the light dim. Those sharp eyes close to him, staring into him, unfolding his thoughts and leafing through each one, quick, careless, no compassion… The curiosity, the fear, piercing him. His throat was raw. His voice was searing in his ears. Vulcans do not scream… They do not scream…

Quiet. They might not come if I am quiet. Stay small. Quiet. Don't scream.

Needles threading through his brain, each cord pulling, the pain bypassing all control. Scream. Quiet. His voice searing in his ears. Take what you want, I do not have it. Take what you want… Scream –

She was thrust out of his mind. Physically she found herself recoiling from the impact with the wall behind her, her head throbbing with the sudden blow and her breath coming in ragged gasps. The tricorder lay open on the floor, the blue light angled upwards, and Spock's scream was fracturing the silence. She pulled herself back to him, touched his arms, careful, so careful, to keep her hands away from his face.

'Shh,' she urged him, tears stinging in her eyes from the pain or the dream or... 'Spock, shh, Spock. They'll hear you…'

The scream choked and retched in his throat and he pressed his hands over his mouth, forcibly trying to stop the sound until it died away to nothing but small, tattered breaths.

'It's all right,' she whispered, instinctively stroking the rock hard muscles of his arm with one hand, lifting the tricorder and scanning for life with the other. 'It's all right. Nothing close to us. It's all right. Shh…'

He stared at her, his eyes wide and strange in the blue light, with some kind of realisation evident in his expression.

'They're telepaths,' she whispered to him. 'I think your telepathic centres have been over-stimulated. You're very receptive to touch telepathy. You've lost the ability to block.'

He swallowed hard, his hands pressed over his mouth still – and then suddenly he twisted away, retching a thin mixture of water and bile onto the floor.

She waited for him as he lay there breathing hard, his stomach spasming but nothing more able to come.

'I touched your face,' she said. 'I'm sorry. I saw your dream.'

He turned back to her, his trembling hands lowered now, his face sheet white. Then he closed his eyes and settled back down onto the floor, his knees pulled up to his chest, one arm wrapped around them and the other around his neck.

Christine waited a while before scanning him. As she suspected, he was not asleep but in a trance-like state, conscious but passive as she had found him earlier. After sharing his dream she did not blame him, and had no intention of administering a sedative again. It was little wonder that his readings showed prolonged sleep deprivation – he had done it to himself to protect himself from the dreams.

She leant back against the wall, leaving the tricorder open now to provide her with a constant light. Her head throbbed and she felt like crying. Suddenly all of the cuts and bruises and scrapes, and the overwhelming tiredness of having been walking and searching and then walking again in darkness for hours overwhelmed her. She dropped her head onto her knees and let herself weep silently, giving up holding herself rigid, giving up trying to forget all the small pains and the jittering stress of this place, and of caring for this psychologically damaged version of Spock.

After a while she lifted her head and saw Spock, eyes open, watching her unwaveringly. She was glad he had retained the ability to awaken himself. She had not been looking forward to having to jolt him out of his trance with cordrazine again.

She gave him a wan smile, wiping the tears away with the heels of her hands.

'It's all right,' she said. 'Just a very human way of dealing with stress.'

He sat up against the wall, hunching his legs up, looking for the first time slightly self-conscious about his nudity. Then he took the tricorder and held it in his hands, staring at the screen as if overcome by a memory he had lost long ago.

He looked up at her, as if he very much wanted to speak but could not bring himself to, and then nodded towards the floor.

She smiled. 'Are you telling me I can sleep?' she asked, and he nodded, lifting the tricorder as if to indicate that he would keep monitoring.

'Okay,' she said uneasily. She had no idea how long it had been since she slept. She had lost track of time.

She huddled down on the floor, grateful that it was reasonably warm down here, and pillowed her head on her hand. Spock had not done that, she realised. A cultural difference, perhaps, or an indication of his mental state that he did not care for comfort?

She closed her eyes. Could she trust him to keep watch? Despite the nightmare, the sleep seemed to have done him good. Just seeing him handle the tricorder felt like a barrier overcome. It seemed like a part of him restored.

His dream images revolved in her head. That beautiful, somehow sinister, iridescent-furred creature and the eerie song that it had produced… The pain tunnelling into his mind, and the knowledge that he would do anything to make it stop. Quiet, don't speak, don't let them hear me…

She drifted into sleep, caught by Spock's fear, her lips sealed closed.