Instead, the young Ernesto is in love with the beautiful but penniless widow Norina. Pasquale refuses to consider such a union and threatens to disinherit his nephew. Pasquale’s friend, Dr. Malatesta, who is also a friend to the young lovers, decides to help them obtain the old man’s consent. He arrives for a visit and pretends to side with Pasquale. He proposes that Pasquale take a wife himself – a woman with all the qualities necessary to make his old age pleasant – Malatesta’s very own “sister,” Sofronia.

Malatesta explains his plans to Norina and arranges to introduce her to Pasquale as Sofronia, a sweet, innocent girl fresh from convent school. Ernesto arrives just as the “marriage” contract is being signed and, to his consternation, is pressed into taking part as a witness. Malatesta quickly takes him aside to explain his scheme. No sooner is the marriage contract signed however, than Sofronia’s behavior dramatically changes. Much to his dismay, she orders Pasquale to buy her clothes and jewels, and demands such high household expenditures that he will assuredly face financial ruin.

As Sofronia leaves to attend the opera that night, she intentionally drops a note in front of Pasquale alluding to a romantic rendezvous later that evening. Incensed, Pasquale sends for Malatesta, who suggests that he threaten Sofronia with the arrival in the household of Ernesto’s bride – Norina. When the plot is revealed, Don Pasquale denounces them all, but relents as Ernesto and Norina beg his forgiveness.