Dorabella and her sister, Fiordiligi, are wealthy Italian tourists on a vacation in Canada. Having arrived at the port of Halifax, they board a train and travel across the country to their hotel. It is there that they meet two dashing Mounties, Ferrando and Guglielmo. In true operatic fashion, the two couples are immediately smitten and fall head over heels in love.

Don Alfonso, a gentleman philosopher, tells the two officers of his doubts in the fidelity of women. He offers them a wager: He will prove that their lovers will be unfaithful. The young men defend their sweethearts and accept the challenge. Meanwhile, Fiordiligi and Dorabella daydream about their lovers. Alfonso arrives and explains that the officers have been summoned to answer the “call of duty” and must depart immediately. After saying goodbye to their lovers, the girls are inconsolable. Despina, the hotel housekeeper, complains about how much work she must do. When the heartbroken sisters arrive, she encourages the girls to enjoy their freedom and find new lovers, but Fiordiligi and Dorabella cannot fathom such a betrayal. Don Alfonso convinces Despina to help him introduce the sisters to two “infatuated young friends” of his, who are in fact Guglielmo and Ferrando in disguise as waltzing Log Drivers. When the new suitors make advances toward the sisters, the girls are outraged and refuse to listen. The boys are confident of winning the bet. The young men pretend to take poison to gain the sisters’ sympathy. Despina and Alfonso go off to fetch help, leaving the two girls to care for the strangers. Despina reappears disguised as a 'doctor' and pretends to heal the boys. When Ferrando and Guglielmo request kisses in order to fully recover, the sisters again reject them, but it is clear that they’re beginning to show interest in the strangers.

Despina chastises Fiordiligi and Dorabella for not knowing how to deal with men. The sisters decide that Despina may be right—there can be no harm in amusing themselves with the handsome strangers. They each choose which man they would like, each picking the other’s boyfriend. On a moonlit walk, Dorabella responds quickly to the disguised Guglielmo’s advances. She accepts a gift and relinquishes her locket with Ferrando’s portrait. Fiordiligi, however, refuses to yield to Ferrando, although she admits to herself that she is torn between her officer and the handsome stranger. Ferrando is certain that they have won the wager. Guglielmo is happy to hear that Fiordiligi has been faithful to him, but when he shows his friend the locket which he took from Dorabella, Ferrando is furious. Fiordiligi condemns Dorabella for her betrayal and resolves to remain true to her officer. Ferrando suddenly appears and declares his love for Fiordiligi with renewed passion. While Guglielmo watches helplessly, she finally accepts. Guglielmo and Ferrando are distraught at their fiancées’ betrayal. Don Alfonso encourages the boys to forgive the women and marry them. After all, their behaviour is only human nature. The sisters have agreed to marry the young strangers, and Despina, impersonating a notary, does the honours. Alfonso suddenly announces that Guglielmo and Ferrando have returned from duty. In a panic, the sisters hide their intended husbands, who return as their real selves and are horrified to discover the marriage contracts. Finally, the boys reveal the entire charade, and Alfonso bids the lovers learn their lesson.