Roger Sartet (Delon) is convicted for the murder of two cops who were after him for the armed robbery of a jewelers' store three months before. On the way to jail he manages to escape thanks to the help of the family of mobster Vittorio Manalese (Gabin). Sartet suggests they steal a jewellery exhibit in Rome worth $50 million, thanks to the blueprints for the exhibit's security system he got from the man who installed it, but Manalese finds out through an American friend (Amedeo Nazarri) that it would be too complicated. Instead, Navarre proposes hijacking the plane due to take the exhibit to New York. As they are preparing for the hijacking, Sartet makes a fatal mistake – he has sex with the wife of Milanese’s eldest son and they are seen by her young son. The hijacking succeeds, but when the Manalese's return to Italy, the boy sees a man and a woman making out on TV and blurts out in front of the whole family that he saw his mom and Sartet do the same. Vittorio doesn't like it one bit, he is Sicilian after all, and decides to cut Sartet out of the money he was due from the jewels. Sartet will try to claim it but Vittorio will have his revenge...