ACT I. In eighteenth-century Naples, the cynical Don Alfonso discusses women with two young officers, Ferrando and Guglielmo. The gallants insist their sweethearts are paragons of virtue (“La mia Dorabella”) and accept Alfonso’s bet that he can prove the ladies fickle if they do as he says for twenty-four hours.
The sisters Fiordiligi and Dorabella compare the merits of their respective beaux, Guglielmo and Ferrando, showing pictures they carry in their lockets (“Ah, guarda, sorella”). Alfonso brings sad news: the young men have been called to their regiment. They appear, and the five make elaborate farewells (“Sento, o Dio”). As soldiers march by, Ferrando and Guglielmo fall in; Fiordiligi, Dorabella and Alfonso sorrowfully wish them a prosperous journey (“Soave sia il vento”). Alfonso, alone, delivers one last jeer at women’s inconstancy.
The maid, Despina, advises her mistresses to forget old lovers with the help of new ones (“In uomini, in soldati”), but Dorabella is outraged at her capricious approach to love (“Smanie implacabili”). When the sisters leave, Alfonso comes to bribe Despina to introduce two foreign friends of his to the ladies. Fiordiligi and Dorabella, returning, are scandalized to see the strangers, whom they do not recognize as their lovers, heavily disguised as Albanians. The newcomers declare their admiration for the ladies, but both repulse them, and Fiordiligi likens her fidelity to a rock (“Come scoglio”). The men are thrilled, but Alfonso warns that the bet isn’t won yet. Ferrando blissfully looks forward to victory and reunion with his love (“Un’aura amorosa”). When he is gone, Despina suggests a plan to Alfonso to win the ladies’ sympathy.
Alone in their garden, the sisters lament the absence of their lovers. Suddenly the “Albanians” stagger in, pretending to have poisoned themselves in despair over their rejection. Alfonso and Despina run for a doctor. Meanwhile, the ladies begin to waver; pity for the strangers will be their undoing. Despina returns, disguised as a doctor using Dr. Mesmer’s invention, the magnet, to draw out the poison, and urging the sisters to nurse the patients as they recover. The men revive (“Dove son?”), but their increased ardor alarms the women, who angrily refuse their demands for a kiss. ACT II. Attending her mistresses, Despina lectures them on how to handle men (“Una donna a quindici anni”). Dorabella is easily persuaded that there is no harm in a little flirtation, and surprisingly, Fiordiligi agrees. They decide who will pair off with whom (“Prenderò quel brunettino”).
The young men have arranged a serenade in the garden. Seeing their wager through, Guglielmo ardently pursues Dorabella (“Il core vi dono”), while Ferrando woos Fiordiligi (“Ah, lo veggio quell’anima bella”); when he leaves, she admits he has touched her heart (“Per pieta”), hoping her absent lover will forgive her. When the men compare notes, Guglielmo is glad to see Fiordiligi apparently standing fast but Ferrando is dismayed that Dorabella has given Guglielmo the locket containing his portrait. Guglielmo decries the waywardness of the fair sex (“Donne mie, la fate a tanti!”). Left alone, Ferrando sighs that he still loves Dorabella, though he feels betrayed (“Tradito, schernito”). Fiordiligi rebukes Dorabella for being fickle, although she admits that in her heart she has succumbed to the stranger. Dorabella coaxes her to give way, saying love is a thief and people get robbed every day (“È amore un ladroncello”). Alone, Fiordiligi decides to drag her sister off to join their sweethearts at the front, but when Ferrando, pursuing the wager, enters and threatens suicide, Fiordiligi gives in. Now Guglielmo is furious, but Alfonso counsels forgiveness; that’s the way women are, he claims (“Tutti accusan le donne”).
A double wedding is arranged between the sisters and the “Albanians.” Alfonso brings in the notary — Despina in another disguise. Just as the ladies have signed the marriage contract, familiar martial strains outside herald the return of the former lovers’ regiment. In panic, the sisters push their intended husbands from the room and go more or less to pieces when the men reappear without their “Albanian”mufti. Ferrando and Guglielmo storm at the ladies when the marriage contract is discovered. But Alfonso explains the deception, reasoning that true happiness lies not in romantic illusion but in accepting things as they are. Agreeing a trick can work both ways, the lovers are reconciled.
