Roma.During a clash between demonstrating laborers (whose fight the students have joined) a policeman and a student are both killed. The investigating magistrate - in charge of the case with two commissioners - wants to believe to the version of the police: the student was killed by one of the laborers, while the policeman would have been killed by Massimo Trotti.

The mysterious Tronche is being escorted to a castle in France. However, during a stop at a motel, he is attacked by Don Lewis who adopts his identity. The castle is the secret hideout of drug-pushing gang. Two of the crooks are killed by an unidentified assailant. While the false Tronche, Jean (head of the gang) and Pierre search the place for the murderer, Jean's lover is killed too. The four survivors are trapped because they are in hiding from the police...

While keeping an eye on his small time crook brother in law, Inspector Nico Giraldi gets involved in a murder case set in the world of Formula One racing. Giraldi is suspended for trying to cover up for his brother in law and becomes afraid his wife and son may be targeted next. Therefore he calls in the help of his childhood friend and chief informant, Venticello.