And here we go. A longer one even, as I saw no logical point to break it up. Hope you enjoy this one. How do you think will they cope? And for how long will they have to?

Even if they had wanted to separate, it would have been nigh impossible for Christine. Manoeuvring Spock's body demanded far more concentration than the simple act of walking had ever done, and Spock's initial clumsiness while walking in her high-heeled shoes suddenly seemed a mirror image of her current struggle. It got slightly easier when she walked faster, and the experience of learning to ride a Terran bicycle came to mind.

She half expected a comment at the erroneous nature of her comparison, but there was no second voice in her mind anymore, and only silence answered her thoughts.

"You pointy-eared sourpuss.", she thought as loudly as she could imagine one could think. Apart from conjuring up a strong image of Dr McCoy, nothing happened, and the reply to her thoughts remained absent, leaving a touch of relief and a tinge of loss.

Having rounded the corner into the hallway by then, she caught sight of the reflective surface of a control panel on the wall. The sight of the Enterprise's executive officer and her doctor was strikingly normal, but the fact that their positions seemed reversed and she saw her own body some feet to the side and not in front of her seemed a cruel illusion.

Spock, in her body, had stopped next to her, evidently waiting for her inspection to end. There was a lot to inspect, and Christine only now got the hint of an idea of how helpless and foreign Spock had felt when he had taken over her body for the first time. Now, she was in control of his body, and that without his mental assistance.

"Are you alright?"

She wheeled around to him and promptly lost her footing. Being 'in control' of his body was probably furthest from the truth, she thought.

He quickly caught her at the forearms and looked up into his own face.

"Obviously not.", he observed and took her by the arm to lead her into the next room.

"I'm sorry, Spock.", Christine murmured sheepishly, leaning on her own body as much as she dared. She had suddenly become aware of the fragility of her body, as she had looked down at it. Spock was familiar enough with it by now, but she was hesitant to lean into it with his body, keeping in mind Vulcan strength, and Spock's height and weight. Thinking about all that did not help her efforts to walk by herself, though. If anything, it made her feel even dizzier all of a sudden.

"Your body is strong. This is not the first time it has supported mine to an extent.", Spock remarked, noticing her hesitation. He looked up at her in what she interpreted as an attempt at a reassuring nod as they rounded the corner into the next room, and Christine relaxed just a bit, letting him lead the way.

The room turned out to be a secondary lab, cluttered with equipment that the next ship was sent to demolish.

Christine sank on a storage container in the middle, as gracefully as she could manage, and probably as clumsy as Spock's body had ever managed to appear.

"If you feel unwell, I can call Dr McCoy over.", he offered.

She shook her head quickly, which turned out to be a bad idea. "No! No, there's no need. We'll just have to wait. And I don't want him fussing over me when there's nothing he can do.", she explained.

Spock nodded in agreement. He would keep an eye on her, but it would make little sense to invoke medical help if the most probable relief to Doctor Chapel's discomfort was to wait a few minutes for the machine to be fixed. His advantage in this situation was solely based on his having had more time to acquaint himself with her body, with her recurring assistance.

He turned to one of the lab desks which was littered with datapads. Surely McCoy's order to not touch any machine would not extend to these.

Some of the pads still had discarded projects saved, some of them dated months back. This desk had apparently been used by a less orderly member of the research team.

He barely skimmed one research proposal on the use of Tribble reproductive genes to multiply humanoid cells, then turned to the next.

"This one is after the interests of Dr McCoy.", he mentioned over his shoulder to Christine. "It's a proposal for the enhancement of transporters to use in the medical field, by storing the biological information of all people in the transporter and having a patient healed by rematerializing him on basis of that information."

Christine only hummed in agreement and let Spock drone on. Maybe he did it to comfort her, maybe he did it to take his mind off their newfound problem, she did not care. She had lowered his head into his hands and closed his eyes. This might be his Vulcan body rebelling against the Human consciousness suddenly intruding. The headache faintly starting to throb seemed almost like a personal attack with that in mind. In any case, she doubted that she had ever felt that faint and ill. She could hear the alien blood rushing within, powered by a heart that was beating more than twice as fast as what she was used to.

Drawing a shaky breath, she tried to suppress the feeling of nausea that had just joined the headache. Why did she suddenly feel so weak? She felt the heartbeat quicken even faster and felt only more feeble. She took another breath, noticing she had held it while listening to the pulse. Breathing faster now, she felt the fluttering feeling of panic creeping up the spine and tingling all over. She had never felt so at the mercy of another body's whims, and it felt as if this one was out to kill her. Why else would she struggle to breathe, have such a fast heartbeat, and barely detectable blood pressure?

She ripped her eyes open and flinched as someone grabbed her firmly by the shoulder.

Spock was bending over her, raising one of her eyebrows.

"I…did you say something?", she murmured.

"I did. I asked if you were well.", he said while letting her arm fall back to her side, but kept hovering over her.

"I don't think I am. I feel weak, and your body's pulse is so fast that I feel like something's wrong, and I have a headache, and I feel nauseous."

This called for Spock to raise both her eyebrows in what she could only describe as a mixture of amusement and concern.

"You mean you are having a panic attack because you are not used to my body's biology?", he asked.

"I…yes."

She hung her head self-consciously. Of course. She, a medical doctor with a major in biology, might have thought about the elevated heart rate and low blood pressure of Vulcans in comparison to Humans. There hadn't been any need to panic about that; it was simple biology. In fact, she could acknowledge now that Spock's pulmonary and cardiac function were in perfect condition, albeit just coming down from that panicked hyperventilation she had driven it to.

The crate gave slightly as Spock sat down next to her. He didn't say anything, just watched, as she breathed consciously and tried to contend herself with the unfamiliar biology.

"If I wasn't coping this badly, I could laugh about this new development.", she grumbled after feeling somewhat better, stretching the arms and legs she had unexpectedly found herself in command of. She'd never noticed just how long Spock's limbs really were.

"You already did.", he remarked, still watching her.

This experience was decidedly more surreal than watching his unconscious body. Christine was looking at his arms and legs with such scrutiny that he would have found invasive had he been in his body. Then, she patted down his torso, and wrapped his arms around his waist, drawing in a sharp breath.

"Are you quite alright?", Spock asked, wondering whether she felt nauseous.

"Oh, yes! It's just so strange, being in your body, it feels so different from mine! Yours is so tall and strong and sturdy, and long and lean. And slim. You've got quite a slim waist!"

She looked down at him, half-expecting a reaction to her outburst. But Spock was only looking back at her with an air of faint bewilderment.

"You have seen my body a considerable number of times before today.", he managed eventually. "You know my anatomical specifications in detail."

"But I've never felt them on myself. It's like wearing your mother's tailored dress!", she exclaimed.

"My mother's dress?"

Christine rolled his eyes and shot him a disapproving glance, finding that it worked extremely well with these eyebrows. Spock did not seem very impressed by it, only raising one of her eyebrows at her.

"It doesn't fit me.", she made sure to clarify. One never knew with this Vulcan if he understood sarcasm or made a point not to. His wearing her body certainly did not help to read him.

He gave his body a cursory glance, looked at her and said: "Hm, yes, it doesn't.", and lowered his eyes to her hands.

Noticing his look, she addressed him again: "I'm curious, how is it for you? You must have noticed obvious differences before now. How do I feel?"

She hoped no one was listening in. Out of context, the things they said would sound positively scandalous. Not that it could make any difference now. She would be highly surprised if she would not get at least a handful of nosy questions by Leonard and Uhura once this was over for good.

Spock scrutinized her hands much as he had done in her quarters yesterday, then wrapped her arms around her torso, squeezing.

"Soft.", he murmured.

"Soft?"

"Yes. You feel…soft."

"And?"

He got the impression that she had expected slightly more than a monosyllabic answer. The amused smirk she fixed him with only reinforced that impression.

"Surprisingly…athletic.", he tried again.

She chuckled and nodded benevolently, saying: "Soft and athletic. I think I can live with that." She never could bring herself to tease Spock as much as Leonard, for instance, did, regardless of how appropriate it would be.

Having been let off the hook, Spock relaxed visibly, continuing his inspection of the room only visually from his position next to her.

But while he seemed to contemplate their surroundings, his thoughts were on the person next to him, and their shared experience. He did not know how to react to Christine's ease around him. Sharing consciousness with him had given her an insight that had broken away the last remnants of insecurity she could have possessed. True, they had inhabited her head together in the past, but this time had been almost companionate. He had felt how she had grown since then. In a way so intimate it had felt vulgar, he had noticed the difference in their mental contact: how composed and confident she was now, in contrast to the chaotic flood of emotions that had practically assaulted his mind the last time. He still found the forced sharing of innermost feelings disturbing and hard to navigate, but her habit to form conscious thoughts and give him a mental lifeline had alleviated the shock slightly.

He knew that her experience had, again, been largely positive. Maybe it was human nature, maybe it was her empathetic character. Whatever the reason, he had felt her give up control so willingly and full of trust as he meditated, letting herself be pulled along without concern, that he had almost told her to stand back. But she had nestled herself safely around him in a way the Vulcan elders would have deemed grossly inappropriate, and he had let her soft Human consciousness fall asleep while basking in the gleam of his meditation. At that moment had he realised how truly unreserved she shared his company, and how unrestrained her way of conversing with him was.

Sudden motion next to him interrupted his train of thought and he turned to the object of his musings. She shuddered again and sent a suffering glance his way while rubbing his bare arms that poked out from under the loose-fitting patient wear.

"I'm cold, Spock."

"That might be resulting from the shock, as well as from Vulcans being adjusted to much higher temperatures than this.", he answered calmly, looking into the dilated pupils of his own eyes.

"You mean you're always cold?", Christine exclaimed, her shuddering stopping abruptly. For some reason the thought of another's discomfort made her forget her own without fail. But this was perhaps not a quality singular to her, but one that many Humans possessed.

Spock shook his head. "That would be an exaggeration. The optimal temperature of my quarters may be higher than yours, but my discomfort with the ships general temperature is not unbearably high. Besides, I have gotten used to it. And I usually wear more layers than just the sickbay attire."

This seemed to satisfy the Doctor's concern for the moment as she fell silent again.

"Well, at least you're wearing your own clothes again. That's a step in the right direction.", she joked after a time, touching the sleeve of the meditation robe her body was still wearing.

"Indeed." He looked down the front of his robe, a comfortingly familiar sight to be wearing it, even though the legs extending out from under it were very obviously not his.

"Spock…your robe…"

"Yes?"

Christine was still holding the sleeve, rubbing it against her fingertips as if she had just felt it for the first time.

"It feels different now. Less…sleek."

"Another attribute of Vulcan biology.", Spock said, indicating his hands.

"Yes, I remember! You have much more nerve endings in your fingertips. I just never thought they were this sensitive.", she said in an amazed tone, taking a closer look at his hands and lightly touching one palm with the fingers of the other hand.

"They have to be. A Vulcan mind-meld would not work without.", Spock explained. "But I doubt you'd be able to initiate a mind-meld, even with the necessary biology at hand. Just as I cannot initiate a meld with your body although my mind is telepathically trained."

She nodded, continuing her close investigation of his hands, being likewise closely watched. To Spock's dismay, she then proceeded to brush his fingertips along the curve of his ears, up to the tip. He shot her a reproachful look but let her inspection continue for the time being. Then she noticed him looking at her and dropped his arms into his lap.

"Oh, I'm sorry!", she burst out. "I got carried away for a second."

"That much was evident."

She only smirked sheepishly and they resumed their shared silence, but just like before, it did not last long.

"What are you planning to do when this is sorted out and you're in your own body?", Christine asked, sending him a smile that he had never dared to imagine on his face.

"Meditate. Rest.", Spock answered. "You?", he asked the Doctor, more out of courtesy than curiosity.

"Shower.", she sighed dreamily, already painting a mental picture. "There's an awful lot of dust around here and I can see an awful lot of it on my body."

"Indeed.", Spock acknowledged, rubbing away a spot of dirt from Dr Chapel's uniform pants. He noticed some dust on the shoulders of his sickbay attire as well and flicked it casually away.

Christine furrowed his brow in what he had learned to recognise as the precursor to some idea or question.

"I wonder…", she began.

"Your questions never cease, do they?", he teased.

"It's gonna be a sad day when they do, Mister.", she retorted, sending him a reprimanding frown.

"Very well.", he relented quickly. "What are you wondering?"

"I wonder how the Captain got the permission to beam back down with an additional crew member that quickly. Or if he did at all."

"I would be surprised if we had any authorisation to be here again or to use the research equipment."

"You mean he didn't ask for permission?"

"He might have asked in the meantime, but I am sure the answer is still pending."

"Yes, that sounds likely, I wouldn't be surprised if it was.", Christine laughed, remembering the occasions in the past when Kirk's bold decisions had not only served them well but also prevented serious harm. A particularly memorable experience had consisted of him changing the Enterprise's course to Vulcan before getting approval from Command, to save Spock's life.

"Sounds like someone's having fun."

The voice from the doorway startled them both as McCoy called out to them, his boyish grin reflecting the good news he was bringing.

"Come on, you two, let's swap you back.", he said, nodding towards the main lab. "Do you need help?", he added, when he saw Spock leaning on Christine as they were getting up from the crate. He had to remind himself, though, that it was actually Christine in Spock's body who was being supported by Spock in Christine's body, and not the other way around.

"I'm fine.", Christine called back. "I'm only feeling a bit dizzy from this Vulcan physiology.", she said, ignoring Spock's look that seemed to say that 'feeling a bit dizzy' was a gross understatement. Gingerly holding on to her own body's arm, she walked the short distance to the main lab, Leonard on her other side watching her warily.

The Captain and Mr Scott were waiting for them as they came back into the room and Spock and Dr Chapel wordlessly took their places at the machine again and waited.

Kirk took in this all too familiar sight and turned to the engineer at the console who was looking at him expectantly.

"Will they be alright after this, Scotty?", he asked.

"I'm an engineer, not a doctor, Jim.", Scotty remarked. "But they'll switch back correctly, I'm sure."

"At least one of them has never been alright, anyway.", Dr McCoy grumbled from behind the Captain.

"Bones, not now.", he admonished, then turned back to the engineer. "Do it, Scotty!"

Scotty flicked the switch; the wall instantly lit up, and the whining noise began to fill the room again.

Christine closed Spock's eyes for what was hopefully the last time and balled his hands into fists. Spock nervously tapped Christine's fingers against her legs, concealed from view by the folds of his meditation robe's sleeves. He met Jim's hopeful glance and closed Christine's eyes against the light that was enveloping them both.

Captain Kirk watched his two officers and friends disappear within the blinding light, reduced to two indistinguishable shadows against the luminescence. He turned away from the gleam, meeting McCoy's and Scotty's looks of apprehension.

Then, the whining stopped and the light ceased, to reveal Spock and Christine Chapel, steadying themselves against the faintly glowing wall.

Doctor McCoy and the Captain stepped closer as soon as they dared, and Jim took Spock by the shoulders.

"Spock?"

"It's me, Jim.", the Vulcan said, with noticeable relief.

"Spock!", Jim exclaimed joyfully and flung himself at Spock, hugging him tightly. Then, he drew back and smiled abashedly. "Sorry, Spock.", he muttered, having forgotten his friend's natural aversion to physical contact during his enthusiasm.

"Quite alright, Jim." Spock nodded, acknowledging his friend's need for physical intimacy, even if just for the sake of not having to admit to his own.

They looked over at the pair of doctors and met Christine's once again starry-eyed smile over Leonard's shoulder who had wrapped her in a hearty embrace.

Scotty, in turn, was still standing at the console, smiling proudly at them and at the machine.

"Well, let's get out of here, shall we?", Jim said, to which his shipmates nodded in agreement.

"The faster the better.", McCoy said. "I still need to do a couple of neural scans and that won't happen when I get lost in the transporter buffer."

"If you get lost, Doctor.", Spock corrected him.

"Well, maybe I only need one.", McCoy muttered quite audibly to himself.

Meanwhile, they all had arranged themselves into beam-up-position, Spock and Christine being supported ever so slightly by the Captain and Dr McCoy, Mr Scott carrying his toolbox and pushing the anti-grav lift.

Kirk flicked open the communicator, deliberately ignoring the bantering of the CMO and Executive Officer, and said: "Kirk to Enterprise. Five to beam up."

The familiar hum of the transporter beam enveloped them, and, in a flurry of sparks, they were gone, leaving behind only the abandoned experiments and the dust.

To be continued (still one more time)...One more to go. I couldn't just leave it there. Thanks for reading this far, for now.

Tell me how you found it so far if you want, and keep your eyes peeled for the next one.