Nemorino is too shy to tell Adina that he loves her, but Belcore boldly asks her to marry him. Nemorino gets some of Dulcamara's secret elixir (merely cheap wine in disguise) to help him woo the young beauty. When the elixir wears off, he can't afford to buy any more. Dulcamara tries to sell it to Adina instead, who then realizes that she doesn't need any elixir to make her love Nemorino.

Full Synopsis

Act I: A group of villagers are finishing their morning harvesting and resting for lunch. One of them, Nemorino, watches Adina, a wealthy beauty, timidly from a distance, too shy to approach her and sad that he has nothing to offer her but his love. At the urging of the group, Adina reads the story of Tristan and Isolde and how Tristan won Isolde's affection with a love potion. She laughs exclaiming that she wished she had the recipe. A regiment of soldiers arrive led by a brash Sergeant Belcore who presents Adina with flowers and asks her to marry him. She is amused by him and promises to consider his offer. The villagers return to work, and Nemorino finds the courage to declare his love for Adina. She tells him she is too capricious to settle down.

In the village, the people welcome the arrival of a stranger, Dr. Dulcamara. He brings with him a supply of patent medicines for sale — potions capable of curing anything. Nemorino asks him if he knows of the magic elixir of love with which Tristan won Isolde. Naturally, Dulcamara has the very thing, selling Nemorino a cheap bottle of Bordeaux wine disguised as love potion. Dulcamara tells him that the potion takes a day to work, but the effect of the alcohol is immediate. Certain that he will win Adina's love tomorrow, Nemorino ignores her. In response, Adina begins to flirt with Belcore and finally agrees to marry him in a week's time, but when orders arrive for Belcore to report to duty by morning, he pushes Adina to marry him that that very evening. Much to Nemorino's alarm, she agrees, but thinking the love potion will change her heart by tomorrow Nemorino begs her to wait. In turn, she invites all the villagers to a party to celebrate the pending wedding.
 
Act II: At the party before her wedding, Adina is upset that Nemorino is nowhere to be seen, but she agrees to sing a duet with Dulcamara about a young girl who rejects a rich man's proposal out of love for a poor boy. When the notary arrives to witness the marriage contract everyone goes inside, leaving Dulcamara alone. Nemorino enters and asks for the doctor's help. Dulcamara says Nemorino must double the amount of potion and offers to sell him another bottle, but Nemorino spent all of his money on the first bottle. Returning, Belcore learns Nemorino is desperate for money, so he convinces the lad to enlist in the regiment to earn enough money for the elixir.

Back in the town, the village girls, having just learned that Nemorino's rich uncle died and made him wealthy, crowd around him. Unaware of his new circumstances, Nemorino thinks that at last Dulcamara's potion is working — as does Dulcamara. Adina sees Nemorino surrounded by girls and becomes jealous. Dulcamara tells Adina that his potion is the reason and offers to sell her a bottle. She is determined to win Nemorino for herself, but she rejects Dulcamara's offer of his elixir. Adina buys back Nemorino's enlistment papers, and when she tells him what she has done, the couple finally admits their love. Belcore takes her decision in stride, fully confident that many more women await him. Finally, the whole village hears of Nemorino's new riches, and Dulcamara announces it is yet another consequence of his magic elixir.