Alright, here is what I have in mind.Something happens, Enterprise going through a hole or facing an unknown entity...and then Jim blacks out and when he wakes up he is in an unknown planet with no sight of his crew or Enterprise.So he looks for them and realizes this world is completely unknown to him and slavery is normal and his whole crew have lost their memory and are now slaves of the rulers of this world.He tries to find his friends, specially Spock and refresh their memory but finds out that his main crew serve in the castle and Spock is the King's favorite and almost impossible to reach.Now he must find a way.It's up to you how he does it.He may succeed using his own method for refrshing memories of his friends and then bringing back the whole crew with a cure or something.
I have lots of ideas but I would like it if you surprise me in any way.For example, I thought of the king's wife who has a thing for Spock and pretends to not like him and secretly wants to take control of the Kingodm and hates the king.
Or there can be a slave girl that falls in love with Jim and helps him or she could be the princess....
As I said, surprise me.This is the idea.Feel free to shape it however you want.
Bonus if Spock is a bottom.
Thank you and forgive my English.It's not my first language.