Act I, Scene 1:  A room in Don Pasquale's house
Don Pasquale's ward and nephew, Ernesto, has refused an arranged marriage, proclaiming his love for Norina.  Don Pasquale, outraged, decides to disinherit the boy and get his own heirs.  To do this he needs a wife, and he has called on the family friend, Dr. Malatesta, to help him find one.  Malatesta, siding with Ernesto and Norina, makes a plan to teach the headstrong Don a lesson.  He glowingly describes to Don Pasquale his beautiful and completely imaginary sister and tells him that the girl is in love with him.  Before long, the old bachelor is convinced he loves the girl and expresses his desire to marry her.  Furthermore, he is prepared to cut Ernesto out of his will.  Unaware that there is a plot afoot, Ernesto grows bitter at the apparent betrayal by his good friend, Malatesta.

Scene 2:  Norina's house
Norina muses to herself about knowing all the tricks to win a man's love.  Malatesta arrives and reveals to Norina his plans for fooling Don Pasquale:  Norina is to pretend to be Malatesta's sister, wed the old bachelor in a fake ceremony, and then drive him so crazy with her whims and demands that he will be eager to find a way out of the unpleasant "marriage."  There is no time to tell Ernesto.

Act II:  Don Pasquale's house
Realizing that he will never be able to marry Norina without his inheritance, Ernesto laments his situation.  When he leaves, Malatesta arrives with Don Pasquale's "bride" and introduces her to the outlandishly dressed old man.  Without further delay, a ceremony takes place, during which Ernesto returns and is forced to witness the contract, when he is finally told what is afoot.  As soon as the mock ceremony ends, Norina turns into a fiery shrew who torments Don Pasquale with her nasty short temper and extravagant ways.

Act III:  Don Pasquale's house
Exquisitely gowned, Norina brazenly leaves the house, and as part of the plan, she drops a letter where Don Pasquale must find it.  It is a love letter from Ernesto, inviting her to a rendezvous in the garden.  Don Pasquale realizes that he cannot endure the situation any longer.  Furious, he calls Malatesta, who promises to fix everything.  Ernesto sings a love song to Norina, who responds fervently.  Don Pasquale springs upon the conspirators, who explain their plot.  Immensely relieved to discover that his marriage has been a sham, Don Pasquale forgives everyone involved and happily gives Norina to Ernesto.