A love triangle between the poor apprentice Mengone, the rich and assured dandy Volpino, and the local apothecary's ward, Grilletta, Lo speziale is a comedy of great warmth and ebullience.

The trouser role of Volpino reminds one of Cherubino in Le nozze di Figaro and the young lovers' use of disguises will call Così fan tutte to mind.

His love for Sempronio's ward Grilletta is the reason, and in the first scene he mixes drugs while making melancholy reflections on his lot, which has led him to a master who buries himself in his newspapers instead of attending to his business, and allowing his apprentices get on as best they may.

The news that an old cousin of his has married his young ward is more interesting to him than all his drugs and pills; he intends to act likewise with Grilletta.

Alone with Mengone, Grilletta encourages her timid lover, whom she likes, but just when he is about to take her hand Sempronio returns, furious to see them so intimate.

Missing a map, he is obliged to leave the room: the young people take advantage of the situation, and when Sempronio, having lost his spectacles, goes to fetch them, Mengone grows bolder and kisses Grilletta.

He is however detained by Volpino, who comes to bribe him by an offer from the Sultan to go to Turkey as apothecary at court, war having broken out in that country.

In the last scene Sempronio receives a letter from Volpino, telling him that the Pasha is to come with a suite of Turks to buy all his medicines at a high price, and to appoint him solemnly as the Sultan's apothecary.