Spock did not want to go into the infirmary. Therefore, he did not. He did not understand his father’s underhanded suggestions that he go to the infirmary to gather the captain himself. Why should he waste time walking when he could call Kirk from his quarters and meet him directly in his ready room? Sarek may believe there to be some symbolism in coming face-to-face with oneself, but at the moment, it was entirely unnecessary. Besides, Spock simply had no wish to do so. It was bad enough to call sickbay knowing what was happening in there. Seeing oneself in the mirror seemed incomparable to seeing oneself as a demon on an infirmary bed.

“Spock to Captain Kirk.”

The first voice to come through the console was not Kirk’s. “LET ME OUTTA HERE! I HAVE TO GO HOME!”

Spock managed not to flinch.

“Kirk here. I hope you’ve got some explanation, Spock.”

“PLEASE LET ME GO! I’VE GOT—“

“My father and I have reached a conclusion,” Spock said evenly, if a bit loudly, trying to ignore the fact that the doctor had said the word please for perhaps the first time since the Vulcan had known him. “If you would meet us in your ready room, we agree to explain.”

“Agree to—never mind. I’ll be up there. Kirk out.”

Spock glanced up at Sarek, who moved toward him. “This is a trial, Spock,” he said in that tone of deep calm that could convince a wild Klingon targ to hear reason. “Like any other trial, it is finite.”

“Perhaps,” Spock said quietly. In the deepest recesses of his emotional genotype, he whispered, But I want to go home, too.

The doors to Kirk’s ready room slid closed with a hiss as the three men entered. Kirk whirled to face Spock and Sarek, hoping he looked firm rather than petulantly angry. “What the hell is going on?”

For a moment, neither Spock nor Sarek seemed willing to explain, in spite of what they had said a moment ago. Then, without word or warning, Sarek crossed the room and halted before the window, gazing out into the stars. Spock, with a glance at his father, turned his passionless face to Kirk. “It seems your doctor was given my katra,” he said.

Kirk noted the term your doctor with irritation. As far as he and Spock had already come, they had run into a bit of a barrier when it came to Kirk's best friend. As well as Kirk got along with both, he still felt almost constantly in the middle of a crossfire between the two, and was never sure if by spending time with one he wasn't betraying the other. At this moment, he was sick of their petty rivalry and would put up with none of this crap. He nodded once, eyes narrowing. “Fine. What the hell does that mean?”

“Or rather, that of my older self,” Spock said as if Kirk hadn’t spoken. “The katra is the essence, everything that is not of the body. It is customary for a Vulcan to transfer their katra to another upon the moment of death, particularly when they are abroad. The Bearer of the Katra is then obligated to return to Vulcan, to Mount Seleya, and give the katra to the repository there.”

“So it’s…” Kirk struggled to swallow the information. It was impossible, so he spat it back out. “It’s like a ghost? You're saying he's possessed by a ghost?”

Spock’s eyes glinted. “It is not a ghost. It is the essence.”

“Okay. Essence. The difference is...?” Were they for real?

Sarek interrupted, but did not turn from the window. “The comparison is not perfect, but neither is it completely inaccurate,” he said. “The human concept of ghosts bears a striking resemblance, in some ways, to the Vulcan concept of the katra. The katra, like the mythological ghost, aches to find eternal peace. However, they remain fundamentally different. While the ghost is typically viewed as incorporeal, it remains nonetheless a physical presence. The katra is an identity, but not precisely an entity. Rather than being a shadow of the Vulcan, it is his very soul, history, and knowledge. It cannot exist separately of a body or of the repository on Mount Seleya, and yet it lives forever.”

“But it aches?” This was too confusing. Kirk was going to have his little Russian genius invent a brain vacuum after this. Oi, my head.

Sarek went quiet. Kirk watched him closely, but the Vulcan only stared out the window, his back to the captain. After several beats of impenetrable silence, he spoke as if from a great distance. “One alive, one dead. Both in pain.”

“Pain?” Kirk’s brows lowered, creasing the skin between them. “Bones didn’t say he was in pain.” His heartbeat picked up as images of a tortured Bones, writhing in pain on a bed in Sickbay, flashed through his mind. Sarek couldn't mean that. “Or wait—you meant Spock’s body and Spock’s…essence? Both of them?”

“The body is simply that—a body,” Spock replied neutrally for his father. “It is a shell. It feels nothing. Dr. McCoy is the bearer of a katra seeking its peace on Mount Seleya. If he were a Vulcan, it would be simple for him to separate his own identity from that of the katra. Because he is not—“

Damn the Vulcan’s arrogance. Kirk got the point, and Spock's over-explaining was only making this harder. “You mean McCoy thinks he’s Spock? The ambassador, Spock?” Kirk resisted the urge to fold his arms, but his hands twitched at his sides.

“That would be an inaccurate assumption.”

“Okay, so tell me what an accurate assumption would be.” Please, Spock, quit making this difficult. I'm not the one you want to punish.

“Some would judge that Dr. McCoy is the ambassador. He carries the living essence of the ambassador in his mind. A Vulcan Bearer would possess the capacity to keep the katra from taking over.”

Kirk's pounding heart was beginning to sink. “And Dr. McCoy can’t do that.”

“No. He cannot.”

Aching for eternal peace. Poor Bones. Kirk fought to keep his face from changing, but he felt his own Adam's apple bob as he swallowed. “What’ll happen to him?”

“The katra will continue for as long as the body lasts.”

“Not the katra. Bones.”

Spock raised an eyebrow, but before he could reply, Sarek turned and spoke. “If Dr. McCoy cannot manufacture an objectivity to shield his mind—and of any of your crew, I suspect he is one of the least capable of this—then he will deteriorate rapidly. It will not take long. Human Bearers have been known to succumb within hours of receiving the katra.”

“Succumb to what?”

“They die, Captain.”

Kirk’s heart leapt into his mouth. Bones? Die? For an instant, he forgot how to breathe. Then, he burst forth with, “Die? Are you kidding me? From what?”

“The katra is capable of rejecting a host in the same way as a body can turn against a transplanted organ, bringing a severe shock to the nervous system.”

Kirk puffed out the air in his lungs in a frustrated, truncated sigh. “Scientifically. What physically happens?”

Sarek's face softened. “Brain death.”

“Yeah, but from what?”

Sarek raised an eyebrow, an older twin of his son. “This has been a subject of much controversy for generations. Not every Vulcan even believes the katra exists.”

You don’t know, Kirk thought acidly, tightening his jaw. Damned Vulcan, just say you don’t know. “But you know this’ll kill him. Dr. McCoy.”

Spock spoke again. “There is no certainty.”

“You just said,” Kirk said, mustering as much patience as he had left, “that Ambassador Spock’s ghost or essence or whatever can only find rest on Mount Mount. Trouble is, Mount Mount doesn't exist. Vulcan doesn't exist.”

Spock and Sarek exchanged sharp glances, both Vulcans tensing almost imperceptibly. Kirk immediately regretted his insensitive phrasing, but before he could apologize, Sarek spoke. “Mount Seleya was a place,” he said evenly. “There will be others. But first, our people must have a home. We must have another Vulcan. Then, there will be another Mount Seleya, another home for the katra of those who have passed on, and Ambassador Spock can be laid to rest—body and soul.”

“That could take months,” Kirk argued.

“Then Dr. McCoy will adapt or die,” Spock said far too calmly.

The Vulcan’s calm was more infuriating to Kirk than his unfeeling statement. “And you don’t give a big enough damn to do something about it?”

“’Damn’ has nothing to do with it. There is nothing that can be done. You must accept what is happening.”

“Why are you accepting it?” Was Spock being this dismissive on purpose? Vulcans could do mind-bending things Kirk didn't even understand. With that, his brain seized on an idea. “Can’t…can’t one of you take it from him? If Vulcans are so much better at it, why don’t you do it?”

Sarek shook his head. “I am afraid it is not so simple, Captain. To transfer a katra from a living body to a repository is far easier than transferring it from a living body to a living body. The ritual has not been performed in so long that most Vulcans believe it to be legend. Most importantly, it would present as much a risk to Dr. McCoy as the wait—perhaps more, as the High Council lacks experience in the ritual.”

“So you’re saying the only option is to find a colony for the refugees—in the next few hours?”

“That time frame is, shall we say, pessimistic,” said Spock. “Not every host experiences rejection. Dr. McCoy seems to be taking things quite well. If he does not reject all sanity and kill himself, or if his body does not experience belated rejection, he may last considerably longer before his nervous system collapses.”

Kirk gnashed his teeth helplessly. Suicide. Great. He’d have to put Bones on suicide watch now. Bones. On suicide watch. “Okay. That would mean giving up on the whole idea of taking back the colony from the Romulans and finding somewhere new for the refugees. Which might’ve been possible a few days ago, when the ambassador was still around to tell us if he had a plan B.”

“In a manner of speaking, the ambassador—“ Spock stopped suddenly, eyebrow raising sharply as if he was intrigued by his own thought.

“—is still around,” Kirk finished, feeling the light bulb go off over his own head. It was suddenly easier to breathe. “He's in Bones’ head. Bones would know if he had a plan B. Spock, you're brilliant.”

Spock inclined his head at the compliment. “But I must remind you, Captain,” he said, “that Dr. McCoy has limited control over what is happening to him. To involuntarily recall the ambassador’s memories is one matter, but—“

“But it’s his only chance,” Kirk broke in. “You can work with him, can’t you? What if you accessed the thing in his head?”

“That is provided the doctor will allow me to mind-meld with him,” Spock pointed out, raising an eyebrow. “Even then, accessing the katra would be inadvisable. It could cause further damage.”

“But you can help him.” Kirk did not phrase that as a question. He was not ready to accept 'no' as an answer.

There was a beat of silence. “I can,” Spock replied. Maybe Kirk was imagining it, but he saw the commander’s lips tighten in unpleasant anticipation. “If he is willing to cooperate.”

“If we explain—“ Kirk cut himself off. Death wasn’t always a motivator for Bones McCoy. There were, in fact, things his obstinate friend would rather die than do. Like participate in a Vulcan mind meld. “Yeah, I don't see it happening. Does he have to cooperate?”

Spock stiffened visibly. “A forced mind-meld is highly immoral and can produce the same psychological effects in humans as forced sexual activity.”

“Okay, that's out,” Kirk said immediately with a slight helpless widening of his eyes. Mind-rape. Wonderful. Gotta remember not to use that term in front of Bones. “We'll see what happens. In the meantime, what do we expect? More of the same?”

Sarek gave a frown, a nod, and a lift of his slanted eyebrows for emphasis. “More of the same. At times, he will be better. At other times, he will be worse. It will be vital for him to rest as much as possible.”

“Yyyyeah,” Kirk said with a dazed chuckle. “I’ll be sure to tell him.” He could imagine Bones, railing against the pair of security guards dragging him back into his quarters for the zillionth time, screaming, There’s people dying, Jim! They need me! Let me go, dammit! I’m a doctor! I have to emphasize my own competence to make up for my inherent sense of helplessness in the face of death! MY PATIENTS NEED ME, JIM! DAMMIT, DAMMIT, I LOVE THE WORD DAMMIT!

“Jim?”

“Yes, Spock?”

“Why are you smiling?”

Kirk forced the corners of his mouth to cooperate. “Never mind.”

Not that Spock could let something like that go. “Considering the situation with Dr. McCoy and the ambassador,” continued the damnable Vulcan, “I believe mirth to be an inappropriate reaction.”

“Forget it, Spock.”

“That would be difficult.”

“Not literally, just…don’t bring it up again.”

“Aye, Captain.” Spock’s face was even more neutral than before, if possible. Kirk had the distinct impression that the Vulcan was making fun of him. “In regards to the doctor?”

Kirk blew out his breath. He already had a bad taste in his mouth from what was to come. “I’ll talk to him first,” he said. While he was not a master of tact, Spock was even worse. “He's my friend. I can explain it to him.”

Spock hesitated, then spoke a little more slowly, as if uncertain he wanted to add to Kirk's suggestion. “Perhaps I should come with you. I can explain the nature of the doctor’s state.”

“He can come to you if he has questions,” Kirk provided, “but I’d like to talk to him myself first. This’ll be a lot for him.”

“It is already a lot for him,” said Sarek, breaking his own silence. “It may be easier to have someone there who can fully explain.”

“Let me remind you, Captain,” Spock added, “the less stress this places on the doctor, the better chance there is of retrieving the ambassador’s katra before he succumbs.”

Kirk glanced sharply at his first officer. “Let me remind you, Commander,” he said softly but firmly, the tone of voice he often found to be the most commanding, “that our priority is Dr. McCoy. If it comes between the ambassador’s ghost and the doctor, we get the doctor the hell out of there.”

“Of course,” Spock said with a nod, “it is logical to give the living priority over the dead, but it will not come to a choice between them. They will both live, or they will both die. There is no saving one or the other.”

Kirk wasn’t convinced Spock was particularly concerned with logic in a case that involved his future self’s essence and a man who, despite his Vulcan control, he clearly didn’t like. In fact, Spock didn't seem at all eager to confront said man, probably because McCoy knew a few more things about the Vulcan than Spock was comfortable with. He wondered if Spock knew Bones had had access to his very detailed medical history for months now. “Let me talk to him first. You can come in later, if you want, but I want to deliver the news. He trusts me.”

“You seem confident.”

“That's a nicer way of putting it than you're used to. Dismissed.”

When the doors to Sickbay hissed open, Kirk blinked to find it was no longer a hellhouse. Doctors and nurses went about their tasks with a degree of calm, even if one nurse had a bruise blossoming on his chin. The only patient lay subdued on a bed, eyes closed, head tilted away from Kirk. My god, Bones. You're not even fighting. The sight almost made Kirk step right back out of the medical bay to gather himself again. They must have sedated him. That's all. He didn't give up, he's just sedated. He glanced up as one of the nurses—the brave, broad one that had been punched in the jaw—approached him with a grim look on his face.

“Captain,” he said with a respectful nod.

“Is he awake?” Kirk asked, voice catching slightly. He cleared his throat.

The nurse nodded. “Come on over,” he said with a slight warning tone to his voice.

Kirk followed the nurse to McCoy's bedside. To his relief, the doctor's face had regained color, and the sheen of sweat over his skin had dried halfway. His eyes were closed, but his breathing was too quick for him to be asleep. The monitor embedded in the wall over McCoy's head showed the man's vitals, and there was a constant, steady, but unusually quick beep to signify his heart rate. Kirk wet his lips. “Bones?”

McCoy's eyelids fluttered open, and his somewhat glassy eyes latched onto the captain like cobras. He tensed suddenly, starting without rising. “Jim!” he hissed. “You gotta help me. You gotta save me from my own staff. These idiots don't know a leukocyte from Luke Skywalker.”

Kirk smiled wryly. Back to his old self, at least. “It's okay, Bones. They won't kill you.”

“You say that, but I know the little gremlins got their eyes on me. Have from day one.”

Kirk glanced up at a nurse. “He's got his sense of humor back.”

The nurse gave him a dry look that Kirk read as Sense of humor? “We gave him an anti-psychotic. I suspect a sudden-onset personality disorder, but the doctor—who you put in charge of his own medical care, sir—won't diagnose himself.”

“If I had a personality disorder, I'd know it!” McCoy spat. “Damn fool. Doesn't fit under any personality disorder.”

Kirk shrugged helplessly. “You could consider it a personality disorder. When you have more than one, you know.” He circled his temple rapidly with his index finger, the universal sign for cuckoo. “Personality disorder.”

McCoy blinked, then his eyes nearly popped out of his head. “What?”

Kirk now tapped his temple with his finger. “Up here, Bones. Ever heard of a crazy thing called a katra?”

“Buncha Vulcan voodoo. They taught it to us at the Academy in the Cultural Diversity course. Mentioned it'd be a complication in dealing with Vulcan hospice patients, them wanting someone there all the time to put a little ghost in a box.”

“Not a box. Your head.”

“You gotta be...wait. My head? What the hell are you tryin' a' say, Jim?” McCoy's accent thickened as he grew more upset. He struggled to raise himself up on his elbows.

Kirk placed a hand on his shoulder, not actually applying pressure and only implying the act of pressing his friend back into the bed. “Spock and Sarek agree that when the ambassador died, he stuck his katra into you. Which sounds...dirty. Really dirty. In fact, don't ever say it that way. Never gonna put it that way again. But basically, you have his soul. In your head.”

McCoy shoved Kirk's hand away. “I get it, you little weasel,” he snarled, struggling to sit up. Suddenly, he looked like someone had hit him with a cement block. His eyes widened and unfocused, and he slumped back against the bed. “Whoa.”

Kirk glanced up in alarm, but the nurse shook his head. “It's the other dose kicking in,” he explained.

“The other dose?”

“He was really bad, sir.”

Kirk looked back down at the doctor, who looked like he was swimming in the thin sheet covering him. Sarek wouldn't like this. Hell, Kirk didn't like it. The fact that McCoy was reacting this badly likely meant the katra was rejecting its host. Kirk tried to swallow the lump forming in his throat. Why would that happen, since Spock had chosen McCoy, specifically? “Bones?”

“Hm?” grunted the doctor.

“You okay?”

McCoy nodded, staring in the general direction of the ceiling. “Pretty good.”

His accent was almost nonexistent, a sure sign that he was calm. Kirk offered a half-smile and squeezed his shoulder, trying not to show his anxiety. “You're gonna be okay. Now. Whaddyou remember about the last time you saw Spock?”

“Damn Vulcan tried to hack into my brain.”

“No, the ambassador. Spock-of-the-future.” Kirk assumed having the ambassador in his head would make McCoy aware of the situation.

“Oh.” McCoy blinked at the ceiling. “Oh. That Spock. So it is...”

“Yep. That Spock. What do you remember, Bones?”

The doctor closed his eyes. There was a long moment of silence, and Kirk nearly stood up and left, thinking his friend had fallen asleep. Then McCoy's hand lifted, as though floating on its own, and brushed Kirk's nose. Kirk resisted the urge to start back and let the doctor grope his face to his heart's content. At last, McCoy broke his silence.

“I remember him...doing this.”

“Rubbing his hand all over my face?”

“No, you little parasite. This.” McCoy arranged his fingers gingerly on Kirk's face, crudely imitating a Vulcan mind meld. “Funny thing is, I remember doing this before. I mean, I remember him doing it. To...to me. Before. Except...we were older. I was old.” A degree of wonderment trickled into the doctor's voice, then he relaxed. His hand fell back to his side, as though the effort of holding it up was too great. “But it happened a long time ago.”

“What do you remember?”

“He was gonna kill himself. I can't...I can't let him kill himself!” McCoy started up suddenly, eyes wide. The heart monitor sped up. Kirk quickly grasped his shoulders and forced him to ease back onto the bed.

“Bones. Spock. Is not. Going. To kill himself.”

McCoy went limp against his pillow, breathing hard. The hand that had been on Kirk's face now flattened against the doctor's sternum, sliding up to the base of his throat. “He did, Jim,” whispered Bones. “I can feel him dying.”

The heart monitor was not slowing. Kirk stared at the doctor in horror. Feel him dying? Kill himself? My god, Bones, do you hear what you're saying? “Bones. Cool it. Did the ambassador--”

McCoy cut him off with a sloppy wave of his hand. “He wasn't...” The doctor's eyes drifted off, and his voice lowered to an eerily familiar tone. “It was long before I became Ambassador. The ship was in danger. I had no choice. Both Mr. Scott and the doctor attempted to stop me. I admit the doctor was not my first choice, but I trusted him with my life. It was logical that I could trust him with my katra. Now I believe I made the right choice. The only person I trust more is you, Jim, but you were not there until it was too late. The doctor was the right choice. The logical choice.” McCoy's eyes raised, narrowed, solemn, relaxed, but with no contempt. It was the same look the ambassador had given Kirk from time to time, when he talked of times past. Kirk barely had time to register it when it disappeared, and McCoy's eyelids shut. The beeping of the heart monitor slowed to an even, steady pace. After a moment, a snore emitted from the doctor.

Kirk bowed his spinning head for a moment, trying to stand up under everything he'd been handed today. Ghosts and the living dead. Welcome to Starfleet. “I thought you gave him a double dose,” Kirk said to the nurse. When he glanced up, the nurse was staring down at the doctor like he had just seen a marshmallow dancing on his chin.

“Um...clearly it doesn't suppress all his symptoms,” stammered the nurse.

If Kirk had had any doubt before, this was enough to shatter it. He's not dealing with symptoms. He's dealing with a person he can't get out of his head. “Well, he's not psychotic. What do you have for multiple personalities?”

“For D.I.D.? Lexorin, but we'll have to wait for the other meds to leave his system.”

“Put him on that and see if it helps. And make him choose a replacement, dammit, even if you have to hold me hostage to get him to do it.”

The nurse grimaced. “Aye, sir.”