A title informs us that the setting is "Italy, 1798," specifically a huge ship whose elaborate riggings and sails Ulmer's camera lovingly tracks in a series of breathtaking compositions. But there's something amiss on the ship, which carries both arms and some upper-class snobs. Into this dramatic setting leaps the masked Captain Sirocco (Louis Hayward), a notorious pirate and leader of a proletarian revolt against an increasingly cruel Neapolitan aristocracy. Sirocco and his band attack the ship from rowboats, confiscate the weapons, and terrorize the snobs. Baron von Holstein (Rudolph Serato), who controls the police and is secretly behind most of the terror wrought on the people. The film gracefully follows the romance of Sirocco and Countess de Lopez, Sirocco's attempts to save the queen , and the escalating revolt, captured in dramatic scenes of the storming of an island and, eventually, the royal palace.