Okay, this is new twist on an old prompt (the original one is not mine) that had once been circulating the K/S sites for a while. The original prompt was that Kirk is assaulted or gets secret Starfleet orders to seduce someone to get valuable information, the entire crew, including Spock, hate Jim because they think he's a cheating bastard.
I want a different take on it.
Here's my challenge.
Some crew member discovers Jim in a "compromising position", and the rumors start flying around the Enterprise that Jim cheated on Spock. The entire crew give their Captain the cold shoulder, and some try to convince Spock to dump his cheating lover. Spock is the only one who refuses to believe that Jim could ever choose to be unfaithful to him, and the Vulcan reasons that it must be a misunderstanding.
When Spock finally confronts his lover for an explanation, Jim 'confesses' that he was actually raped/or following secret Starfleet orders (author's choice), but that he was too ashamed/under orders to keep quiet/whatever to tell Spock the truth until that moment. Jim says that in order for Spock to be rid of any doubts about his integrity, Spock should mind meld with him to see the truth. Spock declines the mind meld, saying that he trusts Jim, and the fact that he even suggested it tells him that Jim's words are true.
Happy ending, right? WRONG!
Turns out Jim really was cheating on Spock the entire time. The whole story about Kirk following secret Starfleet orders or being raped, was just concocted by a panicked Jim on the spot to cover his tracks after getting caught. And Jim, being a gambling man, offered to mind meld with Spock because he figured that the fact that he offered would be enough to convince Spock that Jim was innocent.
Somehow Spock discovers the truth behind Jim's lies. Maybe he walks in on Jim in the middle of round 2 or confessing the truth to someone. Maybe an Admiral tells Spock that Starfleet gave no such orders. Who knows? Feel free to be creative.
When Spock finds out the truth, how will he react? Especially, since he had trusted Jim so completely as to give him the benefit of a doubt, even when the rest of the crew turned against the Captain. Will Jim be repentant for betraying his lover and try to convince Spock he's changed? Will Spock ever forgive him?
Whether this ultimately ends up with a happy ending or a sad ending is up to the author.
I'm totally cool with this taking place in the Abrams verse, though I'll be super impressed if you manage to pull it off and make it believabe in the TOS-verse!