These are the things I remember:
1. Sasuke 'joins' Akatsuki.
2. Itachi rapes him.
3. Sasori teaches/trains him.
4. At one point Sasori tries to kill Sasuke (I think Itachi kills Sasori instead).
side note: I'm not positive, but I think Sasuke does it with Naruto before he leaves. I also think the joining Aktatsuki was a mission from the hokage. Also, I think maybe Itachi violated him with a bar/piece of soap.
That's really all I remember. The story was posted on Fanfiction.net. Sorry it's so vague.