The curtain opens on Domenico Soriano, 50, a neapoletanian wealthy shop-owner raging against Filumena, 48, a former prostitute. They lived together for 26 years as man and wife and she has cheated him, pretending to be near to death, and convincing him to marry her in extremis. In fact Domenico would have married Diana, a young girl, who is in the house pretending to be a nurse. Filumena reveals the real reason for the marriage: she want to create a family for her three children (Umberto, Michele and Riccardo) who have no idea of who is the mother. Domenico is not going to allow this and asks lawyer Nocella to annul the marriage. Filumena speaks to the young men telling them she is their mother.
Filumena accept the defeat but tells Domenico that one of the children is his. All attempts to find out who is his son fail, and Domenico, after 10 months remarries Filumena accepting to be the father of all three.