He’s been looking for an edge for a long time. He knows nothing is ever permanent under the laws of the Empire, that one day your protector will meet their match and you’re back to sinking into the cesspool with everyone else fighting to survive, or worse, stuck under the harsh rule of the successor.
McCoy was only a child when he learnt what life was about. Since then he’s also learnt that you only get two options – you fight and work to get any advantage, or you die. It’s easy as that. He originally started looking for knowledge as his edge, but soon worked out that it was a quicker route to death than standing in the shadows. He’s gone through the stages of submission, of fight, of selling his soul just to get through another day, knowing that there will be people stronger than him, faster, and more capable of working out the twisted mind games that get people up the food chain. That doesn’t mean that he’s ever stopped looking for a way to beat those people.
He turns the small vial of serum in his fingers, as he comes to his decision. The liquid represents years of experiments and planning, something he’s kept from everyone, not a word of what he’s done ever being written or recorded anywhere but in his own head. This liquid didn’t come from the synthesizers or the replicators, just painstaking measurements from the workings of his mind. It represents that edge he’s been searching for.
He has Jim Kirk’s protection. And it’s been good, ever since they met at the academy. Better than good. For the first time McCoy has felt like an equal rather than the prize, or the toy to be used until it’s too worn and ultimately discarded. Kirk represents as much safety as one can get in this fucked up world, but McCoy’s seen the brightest and the best culled and he knows one day that Kirk will fall. All that brilliance is a signal flare to those that want what he has. And it might be arrogant of him, but McCoy knows that he’s also something of Kirk’s that people want. He’s killed people with methods that no-one else has seen, with silent poisons and angry blades that have met no retaliation. His name is known for his own talents, not just because he walks in Kirk’s limelight.
The vial represents his freedom, but he’s not sure he wants the consequences. Not yet, not while Kirk’s still around. McCoy’s selfish enough to want what Kirk gives him – the friendship that goes beyond rank, the partnership that becomes equality the moment the bedroom door closes. He doesn’t want Kirk’s rank, and Jim knows that. He doesn’t want the attention that being Captain of the flagship brings. What he does want is to live without looking over his shoulder and imagining his end in the shadows and the dangers that lurk there.
He’s taken apart hundreds of bodies, some still alive when he started. He’s used it as torture, as a frightening deterrent to his audience, and as a way to learn. He’s the only physician that can claim they’ve seen the insides of every known race. Kirk ensures that he brings McCoy back a present each time they encounter a new species. Kirk will tell anyone that it’s preparation, after all if you know how a body literally ticks, then you know how to silence it. Kirk also knows that McCoy has created many poisons and toxins from those studies, and that is Kirk’s ultimate motive.
McCoy hopes that Kirk hasn’t noticed his particular scrutiny with the psionic races, with the way he studies each synapse and neurotransmitter until he knows exactly how each species uses and controls its psionic powers. He’s broken it down into a chemical combination that he believes will influence his own brain and trigger the dormant psi pathways. This is his edge, his defense and his attack, but it could also be his downfall. The sudden onset of power he has no idea how to control, and no way to predict what will even be triggered, is what is giving him pause. For all his studies and experiments he has no concept of what a flood of thoughts or emotions will do to a human mind, whether it will drive him insane, or worse – make him mad with power.
He’s only created enough serum for one person, and McCoy has no intention of letting it go to anyone else. It’s him or no-one. If he lived in any other world, McCoy would never have started on his quest, but those that thrive, that live, are the ones that are faster, stronger, smarter… more.
McCoy thinks of what it would take to bring Kirk down, and it’s the thought of what that person would be like that has him loading the vial in a hypospray. He hesitates, the hypospray pressed lightly against the skin of his neck. He needs Kirk, but he wants him too, and what trust they've developed. That want is dangerous, but it's all he has. Kirk keeps away McCoy’s challengers. He might not see it, but he’s not foolish enough to think that Kirk’s name alone is what keeps people from trying to take over the CMO’s position, or trying to take him from Kirk.
He’s doing this for himself, but there’s a part of him that knows he’ll do what he can to protect Kirk too. If this works, he needs to ensure that no-one ever finds out what he can do. He’s not going to be anyone’s puppet. Not any more.
There’s a low hiss from the hypospray that breaks the silence of his office. McCoy has enough time to get rid of the physical evidence of what he’s done before he feels the first wave of sensation flow through his head. It tingles, prickles, and then there’s a starburst of warmth before the roar of voices suddenly crashes into him, darkening his vision.