Tout le monde il en a deux (1974)

Valerie watches over her cousin's place while he's away for six months. She spends her first night there reading, playing records, and calling her girlfriend Sophie over. That night, members of a crazed sex cult break in and mistakenly kidnap Sophie. Valerie's cousin, a member of this cult, has some incriminating photos and the leader wants to ruin his life. Valerie and Sophie's friend Fred go to the cult's mansion stronghold to stop all this madness.