Based on Michel Houellebecq's controversial novel, Atomised (aka The Elementary Particles) focuses on Michael and Bruno, two very different half-brothers and their disturbed sexuality. After a chaotic childhood with a hippie mother only caring for her affairs, Michael, a molecular biologist, is more interested in genes than women, while Bruno is obsessed with his sexual desires, but mostly finds his satisfaction with prostitutes. But Bruno's life changes when he gets to know the experienced Christiane. In the meantime, Michael meets Annabelle, the love of his youth, again.
Bruno meets Christiane in a nudist/swinging camp, where he fucks her in a hot tub after she's done with the first guy (1:06:00). They become a steady couple after that. She brings him to a swinger's bar where they swap partners with a couple on his first night (1:15:10, no sex scene shown). On their second trip to the bar, they join an orgy where he watches as a couple of men take turns in fucking her in front of him while another female is sucking his dick (1:23:46).