Following her husband's suicide, Juli (Lili Monori) sees a man on a bus and is immediately attracted to him. He is Gyorgy (Miklos B. Szekely), a tailor who is returning to his hometown after two failed marriages. The two are drawn together by an electric physical passion. Only later do they learn that they are half brother and sister. Guilt over the longstanding incest taboo splits them apart, but a desperate need for each other compels them to resume their relationship.

When Juli becomes pregnant, her mother (Mari Torocsik) reports them to the police. They are tried and convicted. Gyorgy goes to prison for six months, and Juli is given a suspended sentence. They set up a farm and all goes well until she is pregnant again. Gyorgy refuses to let Juli have an abortion; this time, they both serve prison sentences. Hungarian director Zsolt Kedzi-Kovacs states the question at the heart of the film: "Can any time, place, moral, law or power be stronger than the love between two people?" Forbidden Relations is a relentlessly intense film about two individuals obsessed with their right to sexual fulfillment despite the taboo against incest. Mari Torocsik's performance burns bright, giving an added dimension to this dramatic story.