The Bey's wife Elvira is distressed because he no longer loves her. In fact Mustafà orders her to leave him: he plans to give her to his new Italian slave and instructs Haly, the captain of his pirates, to find him instantly, on pain of impalement, a proud young Italian beauty to tame. Lindoro, the Italian slave captured three months ago, laments his separation from his beloved and is not impressed by the Bey's offer of Elvira, though cautiously refraining from rejecting the idea out of hand.
To Haly's relief, an Italian ship is wrecked and among the passengers captured by his corsairs is Isabella, who has been searching for her lover Lindoro, accompanied by Taddeo, an elderly admirer. Momentarily disconcerted by her fate, she quickly collects herself. When Haly announces that she is sure to be the jewel of the Bey's harem, she prepares to use her woman's wiles to get her way.
To save him from being taken away by the pirates, she claims Taddeo as her uncle. They quarrel because of his jealousy of Lindoro (whom he has never met), but in view of their tricky situation decide to make peace.
Zulma, Elvira's confidante, tries to persuade her and Lindoro to agree to the Bey's plan. Mustafà now offers Lindoro his freedom and a passage home to Italy if he will marry Elvira, and Lindoro evades the issue by agreeing to take her with him and think later of marriage. Haly brings the news that an Italian girl, exactly fitting the Bey's specifications, has been captured, and Mustafà prepares to show his prowess at woman taming, peremptorily ordering Elvira to go. Despite his harsh treatment, she still loves him.
Isabella is brought before the Bey and, instantly summing him up as a booby, pretends to be smitten. He is captivated by her.
Taddeo rushes in, and is astonished to find Isabella apparently on such good terms with the Bey who, annoyed at the interruption, orders him impaled. He relents when Isabella again claims Taddeo as her uncle. Elvira, Zulma and Lindoro come to make their farewells, and Lindoro and Isabella are thunderstruck to see one another. Mustaf¦ is puzzled at their reaction, but then thunderstruck on his own account when Isabella, learning of his plan for Elvira, insists that he must not send his wife away. She says she will have Lindoro as her personal slave. All express varying degrees of bewilderment, manifested by ringings and drummings in their heads.
Haly and Zulma try to comfort Elvira with the thought that Mustafà's experiences with Isabella should make him a better husband, as they can see she will lead him a dance. Mustafà sends a message to Isabella that he will take coffee with her. Isabella is distressed at Lindoro's apparent unfaithfulness (since he was preparing to leave with Mustafà has Taddeo invested with the rank of Kaimakan, his role being to smooth the Bey's advances to Isabella. Taddeo, in fear of impalement, is obliged to accept this distasteful role.
Isabella dresses in Turkish costume in preparation for taking coffee with the Bey. She reproves Elvira for being spineless and promises her a lesson on how to control her husband. Mustafà tells Taddeo that when he sneezes, it is a signal that he wishes to be left alone with Isabella, but when the time comes, Taddeo feigns deafness; and when coffee is served Isabella invites Elvira to join the party, to the fury of Mustafà.
Haly reflects that the Bey, despite his experience, is likely to be outwitted by the shrewd Italian girl. Lindoro enlists the support of Taddeo in the escape plan and Taddeo reveals he is the lover, not the uncle of Isabella - to the amusement of Lindoro, who does not reveal his own identity. Lindoro tells Mustafà that Isabella has elected him to the rank of "Pappataci" (a complaisant husband/lover), whose duties are to eat, drink and sleep. Zulma and Haly look forward to the Bey's discomfiture.
Isabella has had the Italian slaves dressed as Pappataci for Mustafà's investiture. She intends to free them all and exhorts them to be brave and look forward to returning to their homeland.
Having made sure that the Bey's servants are given plenty of wine, she has a banquet prepared for Mustafà and instructs him that he must "see and not see, hear and not hear," and concentrate on eating and drinking. She tests him by talking affectionately to Lindoro and Taddeo assists by explaining to the Bey that he must not react -so successfully that when Lindoro and Isabella escape, and Taddeo realises that he too has been duped, he is unable to arouse Mustafà from his complacency. Taddeo swallows his pride and joins the escape.
Only the arrival of Elvira, Zulma and Haly with the news that the slaves are all leaving arouses Mustafà, by which time, his servants being drunk and incapable of pursuit, it is too late to do more than wave to the Italians as they leave. Mustafà decides to be content with his loving wife Elvira and begs her forgiveness.