Don Alfonso is trying to enlighten Ferrando and Guglielmo as to the true nature of women. He places a bet that he can prove their fiancées, Dorabella and Fiordiligi, are not the icons of purity the young men believe them to be. Both sides are confident of victory within twenty-four hours, and during this period Ferrando and Guglielmo agree to do as they are told by Alfonso.
Sisters Fiordiligi and Dorabella are celebrating the virtues of their lovers. Alfonso tells them that their men have been called up and must leave immediately for the front lines of WWI. The men feign a tearful farewell scene and “go off to war. “ The women are devastated but their maid Despina tells them to look on the bright side and have a good time in their absence—in other words, behave exactly as men would do.
Don Alfonso enlists Despina in his scheme, and he presents two “Albanian” friends to the sisters. Neither Fiordiligi nor Dorabella recognize Guglielmo and Ferrando in disguise.
Offended to see the strange men, Fiordiligi and Dorabella are repelled by their advances. They declare fidelity to their lovers. The young men are delighted but Alfonso is still confident in his ultimate triumph.
The sisters continue to grieve for their men at the front. The two Albanians return and, despondent in the women’s rejection, swallow “poison” and collapse. The terrified girls call for Despina, who goes to find a doctor who claims to cure any illness by magnetism. The men revive and believing they are in heaven, demand a kiss from their “angels” Fiordiligi and Dorabella. The sisters rebuff their advances once again.
Despina persuades the sisters to befriend their new admirers. They decide on preferences: Dorabella chooses Guglielmo; Fiordiligi selects Ferrando. Each has instinctively chosen the other’s partner. Dorabella yields to Guglielmo, exchanging lockets as a pledge of fidelity. Meanwhile, Fiordiligi rejects Ferrando.
Ferrando and Guglielmo report on their progress. Ferrando is furious at the infidelity of his fiancée Dorabella.
Despina and Dorabella put pressure on Fiordiligi to have fun. Fiordiligi decides she must run away to join Guglielmo at war, but Ferando confronts her again and she finally yields. Agonized, Guglielmo witnesses it all. Don Alfonso has proven his point and won the bet.
Don Alfonso and Despina arrange for the new couples to be “married” by Despina, disguised as a notary. As the girls sign their names, a military band is heard, signaling that the soldiers have returned unexpectedly. In the confusion, the two men disappear, reemerging without their disguise. Shocked at the evidence of a wedding they swear vengeance on their rivals.
The entire plot is finally revealed. All four lovers’ certainties have been destroyed and no one knows quite what to believe, except that human nature is far more complex than they ever imagined.