Act 1Captain Fracasso and his Hungarian troops are stationed near Cremona. He lodges in the home of Don Cassandro. Captain Fracasso falls in love with Giacinta, and Simone with Ninetta. Fracasso and Giacinta want to marry, as do Simone and Ninetta. But they can't do it without the consent of Cassandro and Polidoro. The two brothers are comfortable with their status quo - they don't want to marry, or to part with their sister. A plan is devised to outwit the brothers, with the help of Rosina. She poses as a naïve simpleton and makes both brothers fall in love with her until they agree to the marriages. Polidoro falls in love with Rosina first and proposes marriage immediately. At first Cassandro is indifferent, but eventually his defences are completely disarmed through Rosina's naïve innocence. So far, the plan is working.
Act 2Polidoro still believes Rosina plans to marry him. Rosina coaches him for a confrontation with his brother. Polidoro demands half of his inheritance from Cassandro. Giacinta fears a quarrel between the brothers, but the others look forward to their fight. Rosina and Fracasso congratulate each other for their successful plan to outdo Cassandro. They continue to engineer the rest of the plot. Simone takes Giacinta into hiding. Fracasso tells the brothers that Giacinta absconded with the family inheritance and ran away. The plan is so successful that Ninetta follows. Simone announces that Ninetta has stolen whatever she could get and also fled. The brothers promise to marry both girls to whoever can bring them back. Fracasso and Simone volunteer.
Act 3Simone catches up with Ninetta and they get married. Giacinta is afraid her brother will not agree to her marrying Fracasso, but he assures her Rosina has taken care of everything. Fracasso and Giacinta pair off. Finally Rosina rejects Polidoro and marries Cassandro. All ends well for everybody except Polidoro.