It ends like this. Spock needs to leave. McCoy needs to talk.
Long-legged strides carry the Vulcan toward the door. Rapid footsteps carry the doctor in front of him.
"We need to talk. Now. I've tried to apologize - god knows I made a mistake, but I'm doing my best. Now I need you to work with me here!" McCoy pants, jaw set. The present is all-consuming, leaving no room to think about anything else.
Spock stares back at him; stares at what he represents. Images swirl through his head - the shameful admission of emotion, fingers around a fragile throat, a relationship jeopardized through careless aggression, Jim's body in the ahn-woon, emotions unrecognized sparking into violence with a few hours provocation. A future branching off into infinite paths, a future where Spock must protect those he loves from himself. Spock does not engage with McCoy. The future is all-consuming, leaving no room to think about anything else.
"I do not wish to continue this conversation at this time." Curt words, though less harsh than the sweeping motion Spock takes to brush by McCoy.
But McCoy will not listen, not to an evasion. The drive has taken him, and it puppeteers him with near-manic energy. McCoy reaches out, and a hand extends to grab Spock's arm, to make him listen.
It is the beginning of the end.
Spock does not mean to harm his human companion. It is simply that human bones are so fragile, and when he instinctively brushes McCoy's arm away, when that distracted, instinctual, overwhelmed, inhumanly strong hand meets a flimsy human wrist the results are not what anyone had intended.
The room is silent, broken only by McCoy's gasp as he tugs his arm against his chest.
But the end has not come yet.
Shocked out of the future, and rooted into the moment, Spock reaches out, an instinctive gesture only desiring to help.
McCoy does not intend to do what he does next. It is simply that his wrist has been broken by that inhuman strength yet again. It is only that he is alone in his medbay and his wrist is broken, and he cannot be blamed for the memory of cold brown eyes on a dispassionate face. It is simply that he has just been hurt, and he does not have time to think.
It is simply… that when Spock reaches out his hand, McCoy takes a step back.
Just one.
But Spock does not know about cold brown eyes. He only knows the slip of the ahn-woon. The fluttering human heartbeat pounding a staccato against his fingertips. He only knows the flash of fear in warm blue eyes, the near-inaudable intake of air, the arm that draws closer to its owner's chest.
This is the end. And Spock and McCoy recognize it as one.
Spock freezes. Straightens.
Frantic, now, in a new way, McCoy reaches out with his uninjured arm. "-Spock!"
But there are no more calculations, now, no more probabilities and options and paths and possibilities. There is only the one path, and all that is left to determine is the quickest way to take it.
Without a word, the Vulcan turns, carefully, and passes the physician to leave the sickbay.
"Spock, you idiot, I'm alright! It's nothing!"
Spock only ducks his head, and then he is gone.