Mustafa, Bey of Algiers, has become weary of his wife Elvira and has made up his mind to remarry her to his Italian slave Lindoro. He dreams about a self-confident Italian lady, whom his corsair officer Haly will soon be bringing for him. As for Lindoro himself, he is longing for his beloved Isabella, whom he had to leave behind in Italy when he was carried off to Algiers. Isabella, also, could never stop thinking of her lover and started to search for him. Before the Algerian coast her ship gets captured by Mustafa’ s corsairs. Haly is delighted to see such a beautiful Italian lady among the booty and sets off to bring her to his master. The men, including Isabella’ s stubborn and jealous admirer Taddeo, have to become slaves. Isabella meanwhile trusts in her feminine virtues, which are to help her to master this difficult situation. She presents Taddeo as her uncle and finally gets permission to take him with her to Mustafa. The latter offers liberty and money to Lindoro, if he takes Elvira and Zulma back to Italy. When Haly announces that the pretty Italian lady has been captured, Mustafa can hardly supress his eagerness and excitement. As soon as possible, Elvira is to leave with Lindoro. Mustafa and the Eunuchs are expecting Isabella’ s arrival. When she enters, Mustafa feels love at first sight. Isabella understands straight away that he will not be a problem for her. Then Lindoro enters with Elvira and Zulma, all three wanting to bid farewell. The young lovers recognize each other in great surprise, but at the same time they take note of their respective companions. Mustafa announces his decision: to separate from Elvira and to put the new Italian in her place. Isabella is furious: she will never tolerate such barbarious behaviour towards his wife, and Lindoro she requires as her personal slave. Otherwise she will never love Mustafa in return. This determined and strong will amazes not only the Bey himself, but everybody else as well. Total confusion breaks out.
Mustafa’ s love is amusing everyone – even Elvira, whose departure has been delayed. Isabella is sad, she believes Lindoro to be unfaithful and to have comforted himself with Mustafa’ s wife. He can however convince her that his feelings are unchanged and thus reconciled, they plan to flee. Meanwhile Taddeo is honoured with the title of „Kaimakan“, but does not feel very comfortable with this new position – guessing Mustafa’s intention: to get Isabella’s love in return. The latter has been invited by Elvira to have coffee with the Bey, who is about to come into her rooms. Now Isabella wants to show Elvira and Zulma how one should treat men. While she is being dressed by the women, her three admirers (Mustafa, Lindoro and Taddeo) are secretly watching the scene. The Bey is completely charmed, not so the jealous Taddeo, who now is presented to her as the new Kamaikan. When Mustafa gives the planned sign – a sneeze – which should announce his desire to stay alone with his love, Taddeo all of a sudden seems to be deaf, and to top it all Isabella encourages Elvira to come and join them. Mustafa feels himself cheated and has an outburst of rage. Haly begins to make fun of his master’ s defeat and expresses his admiration for Italian womens’ cleverness. Taddeo plans to escape to Italy together with Lindoro, whom he still has not recognized as his rival. Mustafa is pacified in that Isabella wishes to elevate him to the order of the „Pappataci“. This title would demand such pleasant duties as eating, drinking and sleeping. The only condition which must be respected: to ignore everything which is going on. Mustafa is flattered. Haly and Zulma bring wine on Isabella’ s instruction, with which they will make Mustafa’ s guard drunk. Clever Isabella has mobilized all Italian slaves in order to prepare the ship for the escape. She tells everybody to be brave and to think lovingly of their homeland. Mustafa appears for the ceremony. Surrounded by the disguised slaves, whom he believes to be real „Pappataci“ he makes his oath. While he is eating and drinking, lost in thought with Taddeo, Isabella and Lindoro set off for Italy. Taddeo realizes to whom Isabella’ s heart really belongs. Not wanting to leave her with his foe, he desperately tries to alarm Mustafa. The latter cannot be disturbed by anything – he keeps eating and remains silent. Now Taddeo, too, leaves Algiers and Mustafa, finally aware of what has taken place, remorsefully returns to his wife, Elvira.