A young woman is writing a series of love letters, telling her lover the story of O, for his entertainment, but also, it seems, as a challenge. O is a fashion photographer, who falls for Rene, a wealthy man who proceeds to take her to the manor of Sir Stephen, where for several weeks, along with other women, she is enslaved in bondage and subject to torture, humiliation, and sexual assault at the hands of Sir Stephen, Rene, and their friends. After a time, Rene takes her back to her old life where she remains in love with him and has learned that when in love, "you are not free at all."

丈夫喜欢拈花惹草，逼得妻子也去找了马夫，被丈夫抓奸在床，于是和马夫比剑决斗，结果……

O is a young, vivacious photographer who falls in love with Rene. While their relationship seems like a storybook romance at first, everything changes when he sends her to a place called Roissy, where women are subjected to intense physical and psychological S&M training to make them the perfect slaves.