Paolino is working to arrange a marriage contract between Elisetta and his patron, Count Robinson, hoping that as soon as Geronimo's older daughter is well married, his marriage to the younger one will be acceptable. Count Robinson has written a letter expressing interest - tempted by Elisetta's substantial dowry - and Geronimo is thrilled to think that his daughter will be a Countess. Fidalma confesses to her niece that she is in love, too, but only reveals in an aside to the audience that she has her eye on Paolino.
When the Count arrives he is disappointed to find that it is not Carolina who has been offered to him. He tells Paolino that he will be content with a smaller dowry and sends him off to arrange the match. Carolina doesn't dare tell the count that she is married, so when she admits she has no lover it excites him further; she tries to convince him she has no desire or qualification to be a countess, but he continues to pursue her. Elisetta accuses them both of betraying her, and the commotion attracts Fidalma who joins Carolina in trying to calm Elisetta; everyone tries at once to explain his or her feelings to the confused and exasperated Geronimo.
Geronimo insists that the Count must honor his contract and marry Elisetta, but the Count refuses. When he offers to accept a smaller dowry with Carolina's hand instead, Geronimo is delighted to save face and money - as long as Elisetta agrees.
Paolino is distraught, and throws himself on Fidalma's mercy, but is stunned to find that she hopes to marry him; he faints, giving her the idea that she returns his emotion and making Carolina think she has been betrayed, but he promises that they will leave the house at dawn and take refuge in the house of a relative.
The Count tells Elisetta all his bad habits and physical defects, hoping she'll reject him, but she stands firm - and he finally confesses that he cannot abide her. Geronimo can't persuade her either. Fidalma suggests sending Carolina to a convent, and Geronimo agrees. Carolina is broken-hearted and tries to confess her predicament to the Count, but they are interrupted by her sister, her aunt and her father who are gleeful at having caught them together, and Geronimo sends Paolino off with a letter to the Mother Superior.
After a brilliant and farcical finale Paolino and Carolina finally confess they have been married for two months; Geronimo and Fidalma are furious, but the Count and Elisetta advise them to forgive the newlyweds, adding that they themselves will marry after all.
The Secret Marriage