A woman meets an intriguing man in a bookstore, she's drawn to him and they end up dating. He has a sister he's close with and they climb mountains together. She finds out he's into bondage, has a very intense relationship with him but starts getting clues he's a murderer. She finds a closet full of ex girlfriends mail and other suspicious things. They end up going to a cabin(?) together where he has a secret bondage room set up(?). She believes he is going to murder her here. She comes across clues of a body buried on the property, then the man's mountaineering sister comes after his girlfriend. The woman realizes the sister is in love with her brother and has been killing his girlfriends.