It was directed by Henri Verneuil and stars Jean Gabin, Lino Ventura and Alain Delon, whose casting has been credited with the film's box office success in France.

In Paris, robber and murderer Roger Sartet escapes from custody with the help of the Manalese, a small, well-organized Sicilian Mafia clan consisting of patriarch Vittorio, his two sons, and his son-in-law.

Sartet pays them with some valuable stamps he had stowed away, and the Manalese hide him in an apartment above the arcade game manufacturing company they own as a front.

Jeanne, the French wife of Vittorio's elder son, looks after Sartet, but he sneaks out to see a prostitute at a hotel and narrowly avoids getting captured by Commissaire Le Goff.

While in prison, Sartet got to know an engineer who worked on the security for a jewelry exhibition in Rome before becoming incarcerated, and he learns the details of the system.

He proposes that the Manalese help him rob the show, but they are dubious of the hot-headed outsider, so Vittorio and his old friend Tony Nicosia, who has lived in New York City for decades, go to the exhibition to check it out.

Warned of Sartet's imminent arrival in the United States, the local police race to the airport, but Jack lands the plane on a new stretch of highway that is not yet open.

Back home in Paris, the Manalese family watch a film in which a couple start to make love, and Roberto exclaims that it looks just like what Sartet was doing with Jeanne.

The film rights to The Sicilian Clan were bought by Henri Verneuil, who teamed with Jacques-Eric Strauss and signed a deal with 20th Century Fox.

[9] As the writing progressed, Verneuil began to feel that the police officer was another strong role, and he decided to cast Lino Ventura, who had made his film debut 15 years earlier in Touchez pas au grisbi, which also starred Gabin.