Arnolphe is a 42-year-old man with an interest in young women. He pays for Agnès's education in a convent until she turns 17 when he moves her to one of his many estates (Arnolphe is wealthy). By insulating her from the world, he hopes to ensure her faithfulness to him. He is desperate not to be rejected by her, and he is highly paranoid that she will find other men to sleep with. He even went so far as trying to control what the nuns taught to the young lady—so paranoid he can't even trust literal nuns. Arnolphe has a friend named Chrysalde who warns him of the dangers of his obsessions, but he does not heed her words.
Horace arrives at Arnolphe's estate where Agnès has begun living, followed by his father and another of Arnolphe's friends, Oronte. Agnès meets Horace, and they both know immediately—it's love at first sight. Horace thinks Arnolphe is someone else and wrongly confides in him all the fun things Agnès and he had done together. He is thrilled about his new little girlfriend, and Arnolphe immediately begins a plan to ensure that Agnès will marry him instead of her new little friend Horace.
As the play continues, Agnès (who, again, is only seventeen) continues to sneak around and hang out with her new boyfriend Horace, to Arnolphe's chagrin. After a few fights, Agnès and Arnolphe miscommunicate, and Agnès believes she has Arnolphe's blessings to marry Horace. When they realize the error, Arnolphe keeps her locked away from Horace.
Horace still doesn't know that "Monsieur de la Souche" is actually just Arnolphe, so when he rightly discovers that Monsieur de la Souche has kidnapped Agnès, he goes to the only person who might be able to help: Arnolphe.
In the last act, Oronte and Enrique arrive at the property and announce that their son and daughter will be married. But, as it turns out, Enrique's daughter is Agnès. Arnolphe has no way to stop the marriage.
