The Thirteenth Reunion (1980)

Ruth, the reporter for the women's section of a magazine, is assigned by her editor to participate in the ten-weeks course of a new weight-loss organization called "Think Thin". According to a letter from a reader, the course is very masochistic and depressing, destroying the self-esteem of the patient. Ruth makes a friend in the course, who dies in a car crash. During the funeral, an employee of the funeral house discloses weird events that are happening in his job. In her investigation, Ruth finds dark and macabre secrets. Originally an episode of British horror anthology TV series, Hammer House of Horror, that later received a feature release in the United States.