Blaine and Kurt become friends, and Finn, in the name of being a good brother, warns Kurt not to get close to Blaine because he thinks Blaine is hitting on Kurt, just trying to have sex with him, and has no interest in being friends with him. Kurt keeps telling Finn he's got nothing to worry about and gets closer and closer to Blaine, while Finn gets more and more paranoid about Blaine's intentions with Kurt.
Eventually Finn starts getting violent and actually hits Kurt. Now Blaine gets really worried, but Kurt doesn't wanna say anything cause he fears it might be too stressful for Burt.
So Kurt transfers to Dalton under the pretense of being afraid of all the bullying in school, but it's actually to get away from Finn. After a couple of months, Kurt and Blaine do get together and, when Kurt gets back home for Christmas break, Finn finally gets really violent with Kurt. Burt and Carole catch him almost killing Kurt, they take them both to the hospital and it turns out Finn has a mental sickness of some sort (I don't remember exactly what), which makes him extremely paranoid.
That's about as far as I read, sounds familiar to anyone?
Found: The Songs Start to Make Sense (great story, I really recommend it to any Klaine fans)