A gang of young "black jackets", led by Frankie, opens a nightclub just above the hideout of a gangster named Morelli who is plotting the heist of the century: the theft of a priceless tiara.

With his friends, Frankie would like to open a club for young people. This initiative greatly disturbs Aldo Morelli, owner of a neighboring cabaret and head of a gang of thugs preparing a big deal: the theft of a tiara worth an immense fortune. As Frankie bothers him, he has it removed. But the American adventurer, Ric Benton, who has a score to settle with Morelli, sides with Frankie's young friends. In fact, it is Ric Benton who recovers the famous tiara and who proposes to exchange it for Frankie. Aldo Morelli thinks he has the upper hand but has forgotten the determination of Ric Benton, Frankie and his gang riding powerful motorcycles.