Geronimo, a wealthy and deaf Bolognese merchant, has two daughters, Elisetta and Carolina, and a sister, Fidalma, who runs the house. Fidalma loves Paolino without realizing that he has been secretly married to Carolina.
Elisetta is to marry Count Robinson, but when he arrives, he falls in love with her sister. Carolina fails to dissuade him. Geronimo remains oblivious.
Geronimo agrees to the count's marriage to Carolina. Paolino is distraught and approaches Fidalma for help. She interprets his pleas as a proposal, causing Paolino to faint into her arms.
Naturally, Carolina enters to see Fidalma cradling the young man and she is only just won round by her husband's protestations of love. The count, endeavouring to distance Elisetta from him, behaves apallingly. Carolina and Paolino try to run off together, but are caught by Elisetta who, assuming the man to be her count, summons the others.
The plot is then unravelled, Geronimo blesses the marriage of Paolino and Carolina, and the count agrees to honour his obligation to Elisetta.