Author's Note: This started out as a five-times fill. I dashed through four sequences, but then I found that stopping at five not only derailed the narrative but also left out one of the most significant violations (Sybok), and forced me to consider a rather trite resolution after the fal-tor-pan. Which is how this turned into a seven-times fic with a slightly more bittersweet ending than usual.
Summary: Seven times McCoy's mind was violated, and one time he didn't have to face it alone.
The first time it happens, McCoy doesn't know enough about telepathy to fill a pamphlet, and his exposure to mind control is limited to novelesque fantasy. He doesn't know why the Archons separate him; perhaps they consider him the least valuable and therefore the most appropriate candidate for being reduced to the level of a mindless automaton.
When Jim asks him later if he remembered the process – tentatively, apprehensively – McCoy had lied and said he did not. When Spock had also asked – clinically, academically – he had told him to fuck off.
The truth he kept to himself, and if he sometimes sat with his back to a bulkhead, wishing he could claw at the inside of his mind to see if any of himself was missing...well, no one else needed to know that.
The second time is worse because it isn't a stranger. He knows the face, however obscured. He knows the smoldering eyes, the hands. He knows the stiff control and relentless will. It's Spock, and in the end it doesn't matter that it's not his Spock.
It hurts like dying, and afterward that's all he thinks about for days, weeks. Sometimes he catches himself just staring off into space, trembling, and it scares him that he's losing time. Trauma is hard to keep hidden, but there's a perverse kind of luck about him. Nobody asks.
And that's possibly what hurts the most; that neither Jim nor Spock notice anything is wrong. At night he presses his knees close to his chest so that all he can do is wheeze, keening. His mind burns, then itches, scarring. He survives, but it feels like a bone that was badly set, because sometimes it still aches.
The third time makes him wonder if something is wrong with him, because he's tired of being pulled aside, singled out, entered and emptied and left with his hands helplessly open, wondering why they'd done this to him.
It's worse because Korob and Sylvia's game is so pointless. Sylvia is the one who does it, and it scraps and tears and they don't even know what they're looking for.
At the end of the mission he's left with bruises from his friend's hands, which he covers with blue fabric and a downturned chin, and a lasting sensation of other people's fingers in his mind, of helpless horror, nakedness.
He makes sure that Scotty and Hikaru receive extensive counseling and feels badly when they recover almost without needing it. 'Something is wrong with me,' he remembers thinking.
It won't be the last time.
Dire circumstances make the fourth time a necessity, and he feels like a coward for being so deeply affected. The others come away from the phantasmagoric Western corral with nothing more than a crooked smile and a good story. McCoy returns to the ship and downs half a bottle of sedatives, and then has to put his fingers down his throat to keep his irrational devastation from depriving the Enterprise of her Chief Medical Officer.
Because Spock hadn't invaded him, not really. Spock had saved his life by pushing away the barriers which made the bullets real. He imagined what Jim would say if he knew – Jim, who took to sharing his mind as easily as though it were a library book. 'You're so uptight, Bones,' he would perhaps remark, laughing like he did when McCoy balked at the edge of the transporter. And as for telling Spock...
Saved me, McCoy thought it over and over. But it didn't stop the old wounds from reopening, or make it any easier to sit up, awake and alone, until he could start sleeping again.
The fifth time he doesn't even understand when it happens, since it follows a more straightforward assault to his subclavian nerve. There's a feeling like an incision being made, deep, deep...but then there's so much else to worry about because Spock is dead and Jim is coming apart and he can barely function because he misses that green-blooded hobgoblin so goddamn badly.
He doesn't sleep for a while, but when he finally goes down, feeble with exhaustion, he dreams of Spock. And for some reason it makes the poorly healed breaks in his mind suppurate, weeping...
He blacks out and upsets Jim and he knows, distantly, that he's losing his mind. It doesn't help when he finds out what Spock had done. He can't resolve his relief and his terrified, selfish revulsion. It makes him hate himself and clutch at the hair near his temples, and when – sometimes – Spock asserts himself and uses his voice or moves his body, somewhere locked inside, McCoy – McCoy – just cries and cries and waits for it to be over or for him to die.
He's almost relieved when the high priestess tells him the fal-tor-pan might kill him. Her fingers feel like daggers of fire, dragging downward, but he's felt that before and is more surprised when, instead of growing hazy, the other presence in his mind loses transparency and becomes something more distinct. Instead it is Spock, his friend Spock, looking back at him.
'You've carried me, Leonard. Thank you,' he says, but there must have been some evidence of the damage, even here, because something suspiciously like sorrow creases the Vulcan's eyes. 'I'm sorry to have caused you pain.'
McCoy feels groggy, insubstantial, but if he had been able to he would have flexed a weary shoulder. 'It's alright. It isn't the first time. Hell, it's not even the first time it was you.'
'My actions were made hastily and with logical intentions. But now I see that they were not without consequence.' There is a pause, and then Spock actually reaches out. Reaches, as though to touch, to connect, to comfort. 'You've been used badly …'
McCoy doesn't know why he draws away. It isn't as though he has anywhere to go, yet something keeps him from being able to accept the gesture. Perhaps it's self-preservation, keeping him from hoping.
They leave Mount Selena, and Spock doesn't even know his name. McCoy's mind feels lacerated, and he doubts that he'll ever be quite the same. The separation was like surgery, and he's left just as scissored and sectioned as Spock, but more subtly. He keeps it to himself, the residual disorientation, the pain. It's not hard to hide. Everyone is preoccupied.
And he has, after all, had plenty of practice.
The moment those eerily familiar dark eyes turn to him, McCoy knows what will happen and his whole soul cries out, as desolate as the plea that would later tear from his lips: "My God, don't do this to me!"
Once again, he faces being singled out, the feeling of another intruding, overwhelming, eclipsing. And it's worse, worse than all the others because his friends witness everything. There are no bars this time, no corridor or iron chains between them, and they still let him be pressed against a pillar and –
The sick, hollow feeling is almost a relief afterwards, and he thinks that if he had been allowed to continue floating, he would have been able to smile just like Uhura, like Sulu, like all the disciples. But Spock doesn't allow him even that, and afterward it's all he can do to stagger after them for the rest of the adventure, trying not to fall.
Sybok remains, even after his body has died in the mad pursuit of god. When they are all safe at home on the Enterprise, McCoy lays his head down against his hands. Feeling flimsy, he lolls, limp, and it's only then that he knows...knows that his mind has become too worthless to even bother defending.
And if he weeps about that, just a little, there's no one there to call him weak.
Spock goes to McCoy after their encounter with Sybok. He has been watching Leonard for a long time, and – though for a while he had forgotten – he knows more intimately than most just how greatly the doctor is in need. It was extraordinarily rare for a non-telepath to suffer a mental attack, and for it to happen more than once...
He finds him in Sickbay, dim in the twilight of the ship's artificial night. Even with the number of refugee disciples now in their care, it is late for him to be working, yet Spock knows that this kind of insomnia is not unusual.
"Leonard," he calls, and the doctor raises his head stiffly. Even in the low lighting, the rims of his eyes appear red from where he has been rubbing them.
"Spock," the man says. "What are you doing here so late?" He attempts to pitch his voice in a manner that transmits annoyance, but this is a defensive gesture, and Spock ignores it with the ease of long practice.
"It is indeed late, but I find that, like you, I am unable to rest."
Suspicious; that is the way the doctor looks at him. He is gazing at Spock with narrowed eyes, emphasizing the creases at their corners. He has also turned his shoulders slightly inward, another involuntary flight response. Spock grieves to see it.
He asks, "Do you think I will hurt you?"
"No!" The response is immediate and vehement, but there is a quality in his tone that countermands the declaration. Considering his history, Spock cannot even call it imprudent. Still, it bothers him that McCoy's demand seems teeny, cracking faintly on the last note when he asks, "What do you want?"
"I'm concerned for you."
'Flabbergasted' is the term that comes to Spock's mind to describe the reaction he receives. It is an archaic Earth expression that well befits this particular human. "Concerned?" the doctor repeats, and it doesn't sound as though he believes it.
"You have long accused me of humanity, Doctor. Does my admission really surprise you?"
McCoy's eyes reach out, clouded blue, searching for Spock's sincerity or falsehood. Finally, something in them quells and he simply states, "I'm fine, Spock."
"You are not. I am concerned for your mind." The words cause the doctor to retreat, but even as he stepped backward, Spock drew nearer. "What Sybok did was inexcusable, not only because of the depth of the intrusion to your privacy, but also because of the harm he may well have caused you. This is of considerable concern, since it will not be the first time you have suffered such an assault."
"Don't." It is a plea, like he had pleaded earlier, when Sybok had not heard him. McCoy repeats, "Don't."
"I cannot ignore the possibility." Spock continues, and though he has always been adverse to causing pain, he waits only a single beat before adding quietly, "It has been ignored long enough."
Perhaps it is all that he does not say, but McCoy's shoulders fall. He appears defeated when he repeats, "What do you want, Spock?"
"I want you to accompany me to Vulcan. I want to see if you might be brought healing."
McCoy laughs in response, and it is a brittle, forsaken sound. "Too little, too late," he responds. "Why even bother trying?"
This is part of the trauma, Spock knows, and he feels just as responsible for it as he does for the physical intrusions. He was the only one equipped to truly understand what the doctor had suffered, and for almost three decades, he had overlooked or ignored it.
'How did you hide so long?' he wonders, but dares not voice it aloud. In light of the circumstances, it would have been cruel. Instead, Spock does something else, closing the breech between them in a way that he never could have in the past.
His hand settles on Leonard's shoulder. Gently, he requests, "Come with me."
Some months later, Spock still has his hand on his friend's shoulder, which is shaking slightly with anxiety. Outside, the world is red, and the heat in the air is a pleasant pressure on his lungs. Yet, as glad as he is to be home, the task ahead is considerable.
The healer intimidates Leonard, Spock can see it from the beginning. Still, he knows that this is the best course of action. McCoy should have been brought here years previous, when there was still a chance to spare him the prolonged suffering he has endured. But that is the past, and though he had grown, Spock is still too much a Vulcan to believe that regret can change anything.
He secures his grip; they are here now.
The episode referred to in the story are as follows:
 – TOS Season 1, Episode 21: "Return of the Archon"
 – TOS Season 2, Episode 04: "Mirror, Mirror."
 – TOS Season 2, Episode 07: "Catspaw"
 – TOS Season 3, Episode 06: "Specter of the Gun"
 – Star Trek II: "The Wrath of Khan"
 – Star Trek III: "The Search for Spock"
 – Star Trek V: "The Final Frontier"