The film starts with the murder of Investigating Judge Vargas in Palermo, amongst a climate of demonstrations, strikes and political tension between the Left and the Christian Democracy (Italy) government. The subsequent investigation failing, the police assign Inspector Rogas (Lino Ventura), a man with a firm faith in the integrity of the judiciary, to solve the case. While he is starting his investigation, two judges are killed. All victims turn out to have worked together on several cases. After Rogas discovers evidence of corruption surrounding the three government officials, he is encouraged by superiors "not to forage after gossip," but to trail the "crazy lunatic who for no reason whatever is going about murdering judges." This near admission of guilt drives Rogas to seek out three men wrongfully convicted by the murdered judges. He is joined by a journalist friend working for a far-left newspaper, Cusan.