Spock had thought many things about Jim Kirk in the early days of their acquaintance. He had thought him to be a cheat, and a disgrace to the Starfleet uniform that he wore. He had considered him to be overly emotional and incurably egotistical, with a disregard for both his own and others' wellbeing that would no doubt get any crew under his command killed. He had thought him to be, as humans would say, 'all hype and no substance', riding on the coat-tails of his dead father and making a mockery of all those values Vulcans hold paramount.

Even after the events surrounding the destruction of the Narada, Spock had remained sceptical. While he could admit that Kirk had displayed a hitherto hidden capacity for logic and leadership, in isolation the events of the battle could not be ruled out as an instance of uncommon good fortune. Indeed, any number of Kirk's risky decisions during those chaotic days could have ended in unmitigated catastrophe.

When he had signed on as First Officer for the Starship Enterprise, he had vowed not to allow himself to be drawn in by Kirk's ever-growing reputation – fuelled by Earth and Starfleet media – as a young hero and roguish genius. His intentions in accepting the position had been as much about monitoring and tempering any outlandish actions taken by the boy Captain as pursuing his older counterpart's claims of a self-defining friendship.

During those first few months of uneasy partnership, Kirk and Spock had clashed over near everything. Where others would co-operate with Kirk's nonsensical and often unorthodox plans, Spock would question and refute and demand they adhere to a route more aligned with regulation. Where Spock would list evidence and probabilities against an idea, Jim would listen and nod and then venture forward with it anyway, often grinning and jesting as he did so. Jim Kirk, it would seem, was everything a Vulcan was not, and their relationship appeared doomed to be one fraught with tension and conflict. They were simply incompatible on a fundamental level.

There was no distinct moment in the course of their interactions that changed this. No point at which either received some revelation regarding the other's behaviour, or fundamental shift in their attitudes. The process was gradual, and involved Spock being forced to confess himself utterly bemused by Kirk's ability to defy the odds in any given situation. Possibilities that Spock would automatically rule out as too risky to undertake, Kirk would embrace and pursue with a staggering success rate. More and more, it became impossible, and furthermore illogical, for Spock to conflate these myriad victories with luck.

Over time, Kirk and Spock began to learn how to communicate with one another without immediately offending or dismissing the other. With increased cohesion and camaraderie among the crew came a mutual interest in capitalising on one another's strengths rather than targeting one other's weaknesses. They started to trust one another, however tentatively, to always work in the best interests of the crew and the mission.

There were several instances Spock could call up from his memory that augmented this trust, of course. Like the time they had crawled together through the ducts of the ship, communicating wordlessly and working together seamlessly to ambush a crew of Orion pirates who had occupied the bridge. Or the time, before Spock and Uhura had ended their romantic association, when Kirk had allowed Spock to be part of negotiations for her release from imprisonment on a hostile planet despite his potential emotional compromise.

There was the time Jim had developed a rare strain of Lutherian flu, and in his feverish state had begun obsessively working his way through the Kobayashi Maru codes again and again, scrawling his calculations across paper and floor and walls. Spock had sat with him all through the night and assisted him in finding the best ways to break his own codes. Or the time a hallucinogenic compound was slipped into Spock's drink at a diplomatic ball, causing all his mental shields to collapse, and Jim had stood over his crumpled and shaking form with his phaser drawn – uncaring of the political scandal he might cause – and threatened to drop anyone who dared to try and touch or even come within ten feet of his First Officer.

They had fought beside one another on enemy ships, beneath alien skies and within hostile territories. And gradually, Spock's attitude towards Jim Kirk had morphed from irate caution, to reluctant admiration, and finally to bewildered yet unashamed fascination.

2.542 years into their five year mission, and Spock and Jim now met for chess on a bi-weekly basis, and ate meals together in the mess hall or one another's quarters most every other night. Somewhere during the course of their association, conversations around missions and crew satisfaction and optimal alterations in engineering had morphed into friendly debates about contemporary theories of physics and Vulcan music and the merits of old Earth literature. It was remarkably pleasant, and while Uhura remained Spock's closest friend, he was quickly coming to realise that Jim was responsible for the reshaping of Spock's world in ways he was not yet sure he understood.

And this was why – Vulcan or no - Spock found himself gripped by absolute and uncharacteristic terror in instances such as these. Because the idea of finishing his shift on the Enterprise bridge, retiring to his quarters and not having Jim one cabin down from him – available for chess or a debate or simply a silent meal – made something twist horribly in his side. Spock had never been one to ground himself in people. Knowledge, ideas, tennets, yes, but not people. So the idea that the loss of just one person might unbalance a self he had thought immune to such changes was not something he knew how to process.

He watched avidly as the crease between McCoy's eyes deepened and he demanded to know what was happening on the other end of the com.

"Jim? What's happening? Are you in pain?"

Jim's voice, when it came through, was stilted and strained.

"B-Bones. Head h-hurts."

Spock felt his heart rate pick up – something he would consider an anomaly were it not for the fact that it seemed to occur whenever Jim was in danger these days. He diverted a small amount of attention to bringing the physical response under control, and eyed McCoy.

The Doctor had his entire upper body bent over the communicator, knuckles white as he gripped the edges of his desk, as if he could launch himself straight through the device to Jim's side. His voice, however, remained clipped and professional.

"Jim, I need you to focus and answer me, alright? Are the muscle spasms only in certain places, or are they throughout your body?"

"Thr-th-thr-." There was a harsh grunt on the other end of the line that betrayed Jim's frustration at his own incoherency. "Throughout," he managed finally.

McCoy closed his eyes, something like despair washing over his features, and Spock reflected briefly on how difficult it must be to hear the suffering of a patient – let alone a friend – and be unable to do anything to alleviate it. He had many quarrels with the Doctor, but the man's devotion to his charges was not one of them.

"Good, Jim, well done," praised McCoy, his professional tone only slightly strained. "And the pain in your head, how bad is it on a scale of one to ten?"

The pained whine that followed McCoy's question had Spock's hands tightening into fists where they rested behind his back. He barely noticed when his fingernails broke the flesh of his palms. After a painful moment of watching McCoy fail to garner a response through the com, he stepped forward.

"Captain? Captain, it is important that you respond to the Doctor. Please Captain. Captain? Jim?"

Both Spock and McCoy jolted like a current had passed through them when Jim finally responded.

"S-Spock?" The voice was slurred and confused, as if Jim wasn't quite certain of what he was answering to, but Spock felt the relief of his reply in every part of his being.

"Yes, Jim. I need you to focus and answer Doctor McCoy's question. How bad is the pain in your head, Jim?"

It became ever more evident that Jim's coherency was failing when the only reply they received was a whispered, "H-hurts."

McCoy stepped back in, elbowing Spock out of the way almost roughly in his haste. Spock neither commented nor cared.

"One to ten, Jimmy, I need a number," demanded McCoy roughly. Spock felt distant surprise at the endearment, but dismissed it swiftly for later processing.

"Eight," came the muffled grunt after a few more tense seconds. "B-b-but it's g-getting w-worse."

McCoy swore viciously. He glanced at Spock and muttered under his breath, "Never heard him admit to more than a six even during his worst migraines."

"B-b-bones?" whispered Jim's voice, and Spock felt another violent twist in his side at his lost tone.

McCoy's head whipped back to the communicator so quickly that Spock heard his neck crack, and his voice when he spoke was low and soothing – almost cooing. It was so very far removed from what he knew of the brash country doctor that he could only stare.

"S'okay, Jim, it's gonna be fine."

There was a shuffling sound from the other side of the communicator – like the slide of jerking limbs against stone floors – and then a distinct thud that had McCoy flinching and Spock's fingernails biting into his palms anew. There was a low keen, followed by Jim's voice – as close to begging as Spock had ever heard it.

"B-B-Bones? I d-don't f-feel s-s-so g-good."

McCoy muffled a dry, angry sob behind his fist, and Spock was unsurprised to see a distinct sheen in the Doctor's eyes. He himself wanted to break something.

McCoy spoke as calmly as Spock believed he was capable of. "It's alright, Jimmy, just listen to me, okay? I need you to put your com unit down by the wall, alright? And then I need you to move a bit away and lie down where it's flat, okay? Make sure you're away from the walls when you lie down. You got that, Jimmy?"

He muttered to Spock under his breath as they waited for Jim to answer, "He's probably going to have a seizure, and if so I don't want the com unit or anything else getting in the way." He turned his eyes on the Vulcan and Spock almost flinched at the raw pain there – McCoy had never been one to hide his true emotions. "There's nothing else I can do for him. Not from up here."

Spock had no response to give that – not when he felt as least as helpless as the Doctor did – so he turned to the com unit instead.

"Jim. Please. You need to listen to Doctor McCoy."

The reply that came through the com was weakened by pain and achingly trusting. "K-kay, Spock."

Spock closed his eyes, momentarily overwhelmed as those two words reached just below his chest and twisted sharply.

There was a sharp clatter that seemed to shudder through both Spock and McCoy in their high-strung state, followed by the agonising sounds of Jim dragging his body across the cave floor. McCoy kept up a steady stream of soothing encouragement, and though Spock did not know what to say, he added to it each time the Doctor glanced his way.

Finally, there was silence, broken by a whimpered, "B-B-Bones."

McCoy bent so near to the com unit that his nose was practically brushing the dials.

"I'm here, Jimmy," he breathed. "Can you tell me how you are? Has anything changed?"

When Jim spoke, Spock almost wished he hadn't replied. His words were fractured and almost incomprehensible, and to hear such a strong man so weak and pained that he could not even force full words past his lips was irrefutably wrong.

"D-d-dark. C's-s-see…h-hur's, B-B-Bones. Sp-p-"

McCoy obviously felt the same way as Spock, because he interrupted swiftly, eyes bloodshot and tortured.

"Sh, Jim, it's okay, just talk when you're able to, alright? Don't force anything. Spock and I are here."

"D'g-go," came the soft plea.

McCoy actually doubled over, as if someone had just struck him in the diaphragm.

"Jesus, kid," he choked out, fist pressed hard enough against his mouth to bruise. He straightened abruptly, clearly trying to regain his shattered composure. "We're not going anywhere. Just breathe for me, kay? Just breathe."

There were are few moments in which all that could be heard from the other end of the line were rough pants, slowing gradually.

There was a soft sound. "B-B-Bones, I th-think-"

And then there only rough grunts, and the horrible sounds of limbs and flesh striking randomly against stone.

"Jim?" cried McCoy, frantic now. "Jim, Jimmy, answer me, goddammit, Jim!"

"He is seizing, Doctor," interjected Spock stiffly, though his own lips felt numbed by the words. "He cannot hear you."

McCoy shoulders jerked, and he rounded on the Vulcan, grief warring with fury in his gaze.

"Don't tell me my job, goddammit! I'm a doctor, I know he's seizing, I know, I just-." He broke off abruptly, covering his face with his hands and raking them up through his hair with enough violence to tear more than a few follicles from his scalp. His eyes were wild, and he seemed torn between breaking into sobs and throwing the com unit across the room.

Oddly enough for the watching Vulcan, he found he could relate. The only reason Spock's hands were not obviously shaking was because they were clasped behind his back, tightly enough to bruise.

They both stood motionless throughout the four minutes of grunts and fleshy thuds emanating from the com unit, gaze trained firmly away from the device and each other. In the endless moment after silence finally fell on the other end of the line, McCoy turned his back on Spock and slumped dejectedly.

"Get out of here, Spock," he rasped. "Go get those damn units prepped and down on that hellhole so that we can figure out what the hell this is and fix it."

Spock hesitated, eyes flicking to the com unit with an expression that McCoy might have found shockingly raw had he been looking, before schooling his features and striding from the room.

Had Spock glanced back, he might have seen the Doctor collapse over the communicator with his head in his hands, already murmuring uselessly to the insensible man on the other side.