It begins when Spock wakes up to a naked and bleeding Jim Kirk in the same bed. He had been in Pon Farr and had planned to let it take him rather than humiliate himself further. In Amok Time, it was shown that he would say or do things he had no recollection of later while in the throes of Pon Farr, and he has no recollection of Kirk coming to him to save his life, or what happened after that, nothing up until the morning when he wakes up. He reacts badly, compounded by the fact that Kirk now feels subconsciously frightened of him due to shock at the violence of the act. They slowly work through misunderstandings of each others' actions and words (e.g. each thinking the other now hates them although they actually love each other, Kirk thinking Spock never wanted to be more than friends and that what he did with Spock was rape, Spock thinking Kirk is lying to make him not leave the ship and that he raped Kirk, that sort of thing) to get together again. TOS please!
Bonus points if you get McCoy to feature prominently too. Whether he knows exactly what's going on or not is up to you. Also bonus points if Spock starts having disturbing erotic dreams of Kirk that may or may not be what transpired during his memory blackout.