Dangerous Liaisons is an apt name for this novel. The epistolary form (meaning that the story is told through letters) outlines a plot that is complicated, because it is an exposé on the French aristocracy and the games the wealthy play to demonstrate power or to manipulate others. Essentially, that's the central idea of the book. It's basically saying "Look at how mean and manipulative rich, powerful people are."
The plot of the store involves ex-lovers who still keep in touch through letters. He, the Vicomte de Valmont (Valmont) is writing to her, the Marquise de Merteuil (Merteuil) about his efforts to seduce a married woman named Madame de Tourvel (Tourvel), while she describes her own fascinations with a young virgin, Cécile de Volanges (Cecile). Cecile has just been released from a monastery for the purposes of courting a spouse, but Merteuil is determined to spoil her by manipulating someone into taking her virginity so that she becomes socially worthless and ostracized. Her motives for this are supposedly connected to her own fascination with power over the innocent people around her, a fascination which Valmont shares. His pursuit of Tourvel is started when Tourvel travels to stay with Valmont's aunt while her husband is away for litigation. The ex lovers have a bet where if he succeeds in seducing the married woman, Merteuil will travel to him and have sex with him.
Merteuil wants Valmont to take the young virgin, but instead he follows through with his intentions for Tourvel. Merteuil settles for this instead: She takes Cecile's love interest, a young music teacher, and seduces him away from her. Instead of following through on her erotic promises to Valmont, Merteuil is jealous that Valmont got what he wanted, but she did not. So she tricks Valmont into walking away from his burgeoning romance, by seducing him more or less, but when he gets there, she doesn't sleep with him. He takes that personally and tells her that he helped to get her lover, the music teacher, back with the virgin girl, Cecile. By the way, in a weird turn of events, Valmont actually does end up taking the virginity of Cecile, which is what Merteuil tells Danceny, the music instructor.
Heartbroken, the young man challenges Valmont to a duel, and he fatally wounds Valmont, who, as he is dying, gives Danceny the letters showing that Merteuil was involved in Cecile's love life.
Then everyone's lives all fall apart. Valmont dies from the wound. Merteuil doesn't die, but she does end up with small pox which leaves her scarred and ugly. Madame de Tourvel dies of a fever. Cecile goes back to her convent, as a pariah and outcast.
