Augusto (Marino Mase) is the oldest son in a dysfunctional Italian family that includes a blind mother (Liliana Gerace), a selfish sister, Giulia (Paola Pitagora), and two epileptic brothers, Alessandro (Lou Castel) and Leone (Pier Luigi Troglio). Augusto is planning to marry Lucia (Jennie MacNeil) despite Giulia's repeated attempts to drive them apart, but cannot do so while taking care of the clan. An angry and unstable Alessandro decides to help Augusto by killing their mother and siblings.