The Sucker (1965) on Netflix

Plot summary

Antoine Maréchal is a Paris shopkeeper who has just set off on his summer vacation when a Rolls-Royce belonging to Léopold Saroyan wrecks his small car. Saroyan, who runs a criminal gang, offers him a way to make up for the ruined trip: collect a white Cadillac convertible in Naples and drive it to Bordeaux, with all expenses paid. Antoine agrees and takes the wheel. The Cadillac carries stolen gems, gold and heroin, among them a diamond called the Youkounkoun, and he knows nothing about any of it. He heads north shadowed by Saroyan's men and, without realizing it, by a rival Italian gang that also knows what the car holds.