Filumena's beauty is not enough: a young prostitute, she meets Don Domenico Soriano (Dummì, Marcello Mastroianni), a wealthy gentleman and womanizer, in a brothel during a bombing raid and the man makes her his lover for years. He uses her to register an apartment, then as caregiver to his invalid mother, then as a worker in his shop and in the management of his house.
When many years later Filomena is a mature woman, he falls in love with his young shop assistant and decides to marry her. At that point, Filomena pretends she's dying, deceiving even the doctor and the priest, and convinces Domenico to marry her on her deathbed. But when the deception is revealed, the man wants to invalidate the contract and Filomena agrees to leave in return for a sum of money and another condition, to invite her sons in Domenico's house, and reveal them she is their mother.
She reveals him that she supported the three boys with money subtracted from him during the years; moreover, she tells him one of them is his son, but is careful not to reveal which. In the end Domenico agrees to recognize all three boys, and marries Filomena.