Dean goes on a hunt while Sam is at Stanford. It's at a secluded place where these people where togas and fast and they praise this one dude who is really just taking their energy and Dean gets brainwashed into thinking his family doesn't love him. John ends up saving him but is all disappointed. I believe it was a multi chapter and I don't recall a sequel but it's been a while.
[sorry for the tags, this new lj is killing me]
Thank you!
(Found: In comments)