Corrado's crusade against the Mafia continues..

Series 4 sees Corrado Cattani continue his personal war with the Mafia. As he investigates the killing of casino-owner Antonio Tindari by Salvatore Frolo, whose wife and daughter were murdered some years earlier, Corrado comes into contact with Tano Carridi, who is aiming with the aid of the Mafia, to gain control of a major insurance company. Cariddi also intends to marry Ester Rasi, the daughter of the company's incorruptible chairman. Cattani tries to dissuade Ester from marrying Cariddi, but when Cariddi blackmails her father, who is forced to commit suicide, Ester decides to stay with him to discover his secrets and get her revenge. Meanwhile Cattani comes across evidence suggesting that Frolo's daughter is not dead after all. As Cariddi finally succeeds in gaining control of the insurance company, events gather pace...