The Depraved (1971)

Lena is alone in the city when her parents are on vacation. She's torn between her innocent boyfriend and the older, more experienced, and sadistic sociopath Helge. She tells Jan about Helge, who gets angry and slaps her, she thereafter runs away and hitchhikes with the promiscuous and friendly couple Lars and Ulla, with whom she goes to Jan's mother's summer cabin. The day after, her boyfriend finds her there and takes her back to the city. Where she yet again is drawn to Helge. Lena's memories, the present and fantasies are frequently mixed.