The plot of La Celestina begins when the young, egotistical nobleman Calisto stumbles upon the garden of Melibea, the daughter of the wealthy and powerful Pleberio, while searching for his lost falcon. When Calisto catches sight of Melibea, he is lovestruck. He begins making declarations about her beauty and virtue, comparing her to a goddess. Melibea, a proud and spirited girl, harshly rejects Calisto’s advances and sends him away. This inciting incident sets Calisto on a path to find his way to Melibea’s heart by whatever means possible. As a nobleman, Calisto could easily court Melibea and try to marry her, but this doesn’t occur to him. He’d rather wallow over his feelings of dejection and bruised ego. Sempronio, Calisto’s clever servant, immediately recognizes that Calisto’s fragile emotional state makes him an easy target of manipulation and offers him a solution—a woman named Celestina.

Celestina, the novel’s antagonist-protagonist, is an old procuress who practices witchcraft and is known to repair women’s bodies to make them appear to be virgins again. Sempronio has a steady relationship with one of Celestina’s prostitutes, Elicia, and knows Celestina well. Sempronio tells Calisto that Celestina can likely work some magic to win Melibea over for him. Because Calisto is lovesick and mad, he agrees to her help. Calisto’s other servant, Pármeno, knows Calisto is heading down a dangerous path by enlisting the help of Celestina, a known scammer, and tries to warn him, but Calisto casts his warnings aside. This insults Pármeno, who is genuinely interested in protecting his masters’ interests and being a loyal servant.

La Celestina is told entirely in dialogue and divided into acts and scenes, but it is not considered a play, and its author always considered it a novel. Unlike typical plays, the characters speak in many asides within earshot of the other characters but their words, spoken for the benefit of the reader, are not overheard by others. Because of this, the reader can access the deep inner thoughts of each of the characters. As such, the rising action of the play concerns much of the lengthy dialogues where the characters fight and argue with each other and reveal their inner goals, desires, and blind spots through their asides to one another. Celestina goes to work finding a way to win Melibea over and promises Sempronio a share of the profits. She casts a spell on a spool of thread and brings it over to Melibea’s house, where she manages to get Melibea alone for a moment to work her magic. The spell works and Melibea agrees to meet Calisto.

Meanwhile, Pármeno and Melibea’s servant Lucrecia grow anxious about their masters’ involvement with Celestina and worry about the bad path they are heading down. They try to interfere with Celestina and prevent her from gaining access to Calisto and Melibea but fail. Celestina, a master observer of human nature and street-smart woman with loads of experience and hard-won intelligence, can manipulate them as well. She promises Pármeno he can have Areúsa, one of her prostitutes whom he’s in love with, and promises Lucrecia some cosmetics to help her win a husband. With these antagonists aside, Celestina makes steady progress in bringing Calisto and Melibea together. Calisto rewards her with gold and a cloak for her successes.

Celestina’s primary antagonist, however, is Sempronio, who matches her in manipulation and savage self-protection. Sempronio becomes the foil to Celestina’s plans to walk away with all the profits for herself, bringing the narration to a climax. When Calisto finally rewards Celestina with a gold chain, Sempronio insists that Celestina share it with him and Pármeno and that she make good on her promise to share the spoils with them. Celestina, arguing that her needs are greater since she is an old woman and that it was her spells, risk-taking, and cleverness that won Melibea over to Calisto, refuses to give them the chain, casually claiming that it was lost. Sempronio, who is much more diabolical than Celestina, stabs and kills Celestina in a murderous rage. The two men are caught immediately and executed for their crime, bringing all the co-conspirators to their demise. Greed serves to undo them all.

The falling action concerns Calisto and Melibea from this point forward. Calisto sleeps with Melibea by using a ladder to climb up to her room and pressuring her to have sex with him, saying he can’t wait any longer. Their lovemaking is almost anticlimactic and a sorry resolution to Melibea’s ferocious attempts earlier in the novel to stave off Calisto’s advances. On Calisto’s way out of her house, however, the ladder gives way, and he falls to his death. Melibea, distraught that her lover is dead and her reputation undone, kills herself in front of her father by leaping from the top of a tower. Pleberio, her father, is left to bemoan his sorry state, mouthing Celestina’s proverbs earlier that wealth can’t protect one from tragedy and that having riches in old age without an heir is no better or worse than being poor and suffering the aches and pains of old age without the money to make them easier to bear. The perils of falling prey to the throes of lovesickness are shown to be great and able to undo anyone, rich or poor.