In Italy in the Sixties, a gang of American thieves arrive in Naples to steal the famous Treasure of San Gennaro. However the Americans do not know how to move in the picturesque town, because for them the customs of the natives are too weird and incomprehensible. So the two men and the girl (the gang members) go to a prison, following the advice of a friend. There they would find, the man who would assist them in their case, a certain Don Vincenzo, who is a famous thief in the city. However, since he is known by everyone in the prison, he is treated by the guards as a gentleman and with respect. The Americans, when they see this type of treatment, which would be impossible in their country, are quite stunned. Don Vincenzo warmly receives them and advises them to go to Naples and look for a certain Armandino Girasole, known as "Dudù". He says that Dudù is a young thief by profession and he could help them. But the Americans, do not reveal to Don Vincenzo what they intend to steal. They meet Dudù and he agrees to work with them.