Elvira complains to Zulma that her husband, Mustafa, is no longer in love with her. Mustafa rejects Elvira’s attempts to rekindle his ardor. He orders Ali, his henchman, to have Elvira married off to Lindoro, a recently captured slave, and to find a lusty young Italian woman to be his new wife.

Lindoro pines for Isabella, whom he has not seen for many months. Mustafa offers him a wife who combines beauty, wealth and kindness, but will not divulge her name.

Searching for Lindoro, Isabella and her traveling companion Taddeo are forced by a storm to seek refuge in Algiers. They are captured by Mustafa’s men. Ali discovers that Isabella is a genuine Italian woman and predicts that she will become the new star of the harem, much to Taddeo’s jealousy.

Lindoro agrees to marry Elvira, in exchange for his freedom and passage to Italy, just as Ali announces the arrival of the Italian girl and her “uncle” Taddeo. Mustafa falls immediately in love with Isabella and orders that the inconvenient uncle be impaled on the stake forthwith. Persuaded by Isabella’s charms, Mustafa agrees to make Lindoro her personal slave and to commute Taddeo’s execution.

Isabella reassures Lindoro of her faithfulness and plots their escape. To flatter Isabella, Mustafa appoints Taddeo a “Grand Kaimakan,” whose requirements include having “the strength of the lion, the guile of the serpent, and a set of good teeth.”

Isabella rebukes Elvira for meekly accepting Mustafa’s transgressions and vows to teach him a lesson. Knowing that all three men are observing, Isabella dons a seductive costume and sings of her love for an unnamed treasure, further inflaming the passions of the eavesdroppers.

Lindoro and Taddeo tell Mustafa that Isabella in turn wishes to honor him by making him a “Pappataci.” His duties will consist of making love, eating, drinking, sleeping, and never quarrelling. Mustafa enthusiastically agrees.

Isabella explains to the Italian captives that the “Pappataci” induction ceremony will actually be a ruse for them to escape. As the ceremony progresses, Mustafa tries to maintain his new regimen of eating, drinking, and silence, but eventually realizes that the Italians have escaped. Chastised, he vows to become a loving husband to Elvira.