The film is based upon the true and tragic events, which took place in Naples in July 1647.
The historical background are the misgovernment and fiscal oppression having aroused much discontent throughout the two Sicilies, at that time viceroyalty of the Spanish Kingdom.
The population of Naples, exploited by the greedy viceroy, the Duke D’Arcos, lives in deepest misery and without any hope of altering their destiny until the appearance of Masaniello, an Amalfi fisherman, young, handsome and courageous. With the help of his friends and allies, known in jail he becomes the leader of the Neapolitan citizens during a violent riot beginning in the 7th of July at the city gates between the fruit-vendors of the environs and the customs officers.
But the glimpse of radical change will not last for long.
Through intrigues, corruption, blackmail and personal sorrow for his beloved Bernardina Masaniello will become rapidly insane. He is murdered 10 days after the outbreak of the riot while haranguing a mob on the market-place on the 16th of July 1647.