Tina is on trial for the murder of her lover, Gino. The violent nature of their relationship, revealed in the trial, seems to make obvious that she accidentally killed him during a fight. The lone female jury member compares her life to Tina's and, believing her to be innocent, sets out on her own to find a missing witness that can prove Tina's innocence.

Set in Naples at the end of the 19th century, I Guappi tells the story of a strange friendship between the powerful and charismatic Camorra boss, Don Gaetano (Fabio Testi), and one of the many scugnizzi who grew up on the streets, Nicola Bellizzi (Franco Nero). Nicola, thanks to Don Gaetano's protection, becomes first an honoured picciotto of the Camorra and then a lawyer. He tries to break away from his 'family', but falls back into a life of crime and violence.