Hungry Young Women (1974)

Richard discovers, by chance, that the wife of an atomic scientist has an affair, and that their son was driving a car without a driving licence, and drunk. Since Richard is a person with a devilish mind, he shows up at the scientist's home with his girlfriend, whom he presents as his sister, and sets in. Using his 'weapons' to pressure every person in the house, he gets all the sex he wants, until everybody is changing partners with everyone else...