In a small town, citizens come back from work and enjoy their time by watching TV. They are fond of love affairs that they can watch in TV series. Nemorino, a young man in loved with Adina, complains about the fact that because of his poverty, the only thing he can offer to his beloved is his love. Adina comments with her friends the story of “Tristan and Isolde”, telling them about how Tristan conquered Isolde’s heart: he gave Isolde a magic potion to make her fall in love with him. Sergeant Belcore comes with his soldiers. His vanity amuses Adina, but that doesn’t prevent him to propose to her. Adina tells him that she must think about his proposal. Nemorino confesses his love to Adina, but she tells him that he would better take care of his uncle, seriously ill, rather than declare his love, because she wants to be “free like the air”.
Dulcamara – a “dreams salesman”, actually a charlatan ready to enterprise any business arrives in town. Nemorino asks him if he has the love potion from the “Tristan and Isolde” story. Dulcamara gives him some fake liquid prepared on the moment. Nemorino spends all his money on it and drinks it. As he is certain now that he will conquer Adina, Nemorino pretends he’s unmoved by her. To punish him, she flirts with Belcore, who tries to convince her to marry him at once. As he is afraid of this plan, Nemorino begs Adina to wait another day, but she ignores him and invites everybody to the wedding. Nemorino runs away, complaining that he had been ruined by Dulcamara’s potion.
The preparations for the wedding take place. Dulcamara, self-proclaimed marshal, sits with the bridal couple. Adina’s thoughts are distracted by Dulcamara, who suggests them to sing a barcarole. When the duet finishes, Adina leaves with Belcore to sign the wedding contract and the guests leave too. Nemorino begs Dulcamara to sell him more love potion but he has no money. Belcore comes back, angry that Adina postponed the wedding until later that night. He asks Nemorino why is he sad. The young man tells him about his money problems, and the sergeant convinces him to join the army, thus getting the money given for volunteers. Belcore gives him the uniform and the money with which he will buy more love potion.
The guests at the wedding understand from Gianetta that Nemorino’s uncle died and left all his fortune to his nephew. When the young man comes back, dizzy because of … the potion, without knowing he’s now rich, the girls are fond of him and he thinks that’s the effect of the potion. Adina and Dulcamara find him surrounded by the beautiful girls and Adina is angry. Trying to sell her the potion, Dulcamara tells everybody that Nemorino’s success is due to it. Adina rejects the idea of drinking the potion and says that she will conquer Nemorino’s heart with her charms. Alone, Nemorino is deeply touched by her love and by the fact that he believes to have seen a tear on her cheek, but, when she comes back, he hides his real feelings. Adina confesses her love to Nemorino.
Belcore finds that Adina is now engaged to Nemorino. He accepts the idea and is certain that thousands of women will be in love with him. Telling everybody that Nemorino’s hapiness is the effect of the love potion, Dulcamara sells them more bottles.