Daaaaaaamn. I just read a fic that blew me away. Dark, but not violent. It's a Hermione fic (yay Hermione fic!) about Hermione being trapped as a prisoner-of-war. She isn't tortured, she isn't abused, she's just... left alone in a cell. For Hermione, I think that would be the worst torment of all. No books, no friends, just herself, slowly losing her mind.
And then Ginny joins her, and everything and nothing changes.