The first part of the novel details the rivalry between Alovisa and Amena, two upper-class young women, for the Count D'Elmont's attention. The narrator mentions the "custom which forbids women to make a declaration of their thoughts." This is important to both the plot and the theme of the novel.[4] Alovisa writes an unsigned letter to D'Elmont. This inadvertently leads D'Elmont to court Amena instead. Amena's father refuses to allow his daughter to continue meeting with D'Elmont without a proposal of marriage. During one of their secret meetings, the pair are compromised by the intervention of Alovisa's servant, Charlo, who awakens Amena's household. Alovisa feigns desire to help the pair by allowing them to meet in her apartment; however, Alovisa colludes with Amena's father to ship Amena off to a convent in the countryside. D'Elmont, in the meanwhile, has left to receive his brother, Chevalier Brillian. During the course of their conversation, it is revealed that the Chevalier has fallen in love with Alovisa's sister Ansellina (who resides in Amiens).
Part the Second deals with D'Elmont's falling in "true" love with Melliora, a girl entrusted in his care. At the first sight of "the matchless Melliora", his "impregnable" heart "surrendered".[5] The Baron D'Espernay, a close friend of D'Elmont, helps him plot to seduce Melliora—in part because he desires Alovisa for himself. D'Espernay plans a ball, during which D'Elmont is arranged to have access to Melliora, but Melantha, D'Espernay's sister, is enamored with D'Elmont and takes Melliora's room. When D'Elmont enters what he thinks is Melliora's chamber, he instead ravishes the too-willing Melantha. Alovisa, certain that D'Espernay can help her discover the identity of her husband's lover, agrees to trade sexual favors for this knowledge.[6] In the chaos of the evening, Alovisa ends up running into D'Elmont's sword.
Part the Third commences with the aftermath of Alovisa's death; D'Elmont ends up in Italy, yearning endlessly for Melliora, while Melliora returns to the monastery where she was educated. Later, D'Elmont intervenes to rescue a stranger from certain death, killing a masked bravo, or "hired murderer", and narrowly escaping with his own life.[7] To avoid being implicated, D'Elmont flees, stumbling into a garden belonging to his secret admirer. D'Elmont is confronted by Melliora's brother, Frankville, for tarnishing her reputation. Frankville is revealed to be the stranger whose life D'Elmont saved earlier on. Despite being affianced to Violetta (the chaste "good" woman), Frankville had fallen in love with a woman named Camilla, inciting the vengeance of Violetta's villainous father Cittolini, who is described as a "possessor of immense riches".[8] D'Elmont attempts to assist Frankville by secretly delivering a letter to Camilla, who lives with Ciamara, the temptress who wrote to D'Elmont. Ciamara (the lusty "bad" woman) attempts to seduce D'Elmont when he mistakes her for Camilla, and this causes Frankville to spurn Camilla. Attempting to rectify this confusion, D'Elmont presents himself to Ciamara as a decoy long enough for Frankville to forcibly gain access to Camilla's quarters. But Camilla is unmoved by Frankville's pleading, and Frankville and D'Elmont narrowly escape an attack from Ciamara's servants. While Violetta was engaged to Frankville, she inevitably falls in love with D'Elmont and seeks to reunite Frankville and Camilla.
Receiving word that Melliora has been kidnapped from the monastery, and learning through Violetta of Ciamara and Cittolini's revenge plot, D'Elmont, Frankville, and Camilla flee Rome, accompanied by Fidelio, who is actually Violetta disguised as a pageboy. They learn that Ciamara had poisoned herself out of grief, and Violetta's vengeful father has also died. En route to Paris, the travelers—burdened by Fidelio who has fallen ill—take shelter from a storm with a wealthy gentleman, the Marquess D’Saguillier. D'Elmont is surprised in bed by Melliora, who reveals the events leading to her kidnapping: Betrothed to Melliora's friend, Charlotta, the Marquess instead desired Melliora and abducted her. Melliora secures her own freedom to leave with D'Elmont through an elaborate plot. Meanwhile, Fidelio is revealed to be Violetta, and she professes her undying love for D'Elmont on her deathbed. Violetta's fidelity is rewarded, as the Marquess D'Saguillier and Charlotta, Frankville and Camilla, and D'elmont and Melliora are wed. D'Elmont returns to Paris, where he is reunited with his brother. D'Elmont and Melliora are "still living, ... great and lovely examples of conjugal affection."[9]
