The narrator introduces Doña María, Marquesa de Montemayor, whose letters are now revered examples of Spanish literature. He warns, however, that biographers have wrongly attributed to her person the graces evident in her writing.

Born to a wealthy cloth merchant in Lima, Doña María was physically unattractive and stuttered. Her mother subjected her to constant criticism and forced her to wear excessive jewelry in public. Despite her resistance to marriage, she was compelled at age 26 to marry an impoverished nobleman. The wedding was marked by the guests’ open mockery.

When Doña María gave birth to an exceptional daughter, Clara, she developed an overwhelming attachment to the child. Clara, however, was emotionally distant and “intellectual.” By age eight, Clara corrected her mother’s speech and viewed her with disgust. The frightened marquesa responded with anxious attention that only drove Clara further away. At the first opportunity, Clara accepted a marriage proposal that required her to move to Spain, placing her six months away by correspondence.

Left alone in Lima, the marquesa withdrew into herself. Her personal grooming declined, and she developed a habit of talking to herself in public. She also began drinking to cope with sleepless nights, and the city came to regard her as an object of ridicule. She was denounced to the Inquisition three times but escaped punishment due to her son-in-law’s influence in Spain and sympathetic friends at the viceregal court. Clara, meanwhile, received a generous allowance but lived extravagantly, becoming a major patron of arts and sciences at the Spanish court.

Four years after Clara’s departure, the marquesa visited Spain. Both women resolved to be patient, but the visit was disastrous. Each tormented the other until the marquesa left abruptly one morning and returned to Peru. From that point forward, letters became the sole vehicle for their relationship.

The marquesa deliberately cultivated her literary talent to win her daughter’s attention. She forced herself into Lima society to gather material, studied great works of Spanish literature, and spent nights composing and revising her letters. However, Clara barely read these letters; it was her husband, the Conde, who preserved them. Even now, the narrator argues, critics mistake style for substance, missing that the letters were primarily an expression of feeling.

The marquesa’s unrequited love gradually eroded her beliefs. She lost her religious faith and came to believe that all human relationships were governed by selfishness, recognizing that even her own love for Clara was tainted with possessiveness.

The famous Letter XXII was written after an evening at the theater during which the marquesa saw the celebrated actress Camila Perichole perform. It describes the marquesa’s fantastical efforts to secure a gold chain for her daughter to present to the king of Spain and recounts Lima court gossip: The viceroy canceled a public engagement and summoned Camila, who was always accompanied by a mysterious man called Uncle Pío. It does not explain that during the intermission of the performance, Camila improvised songs mocking the marquesa’s appearance, drinking, and her daughter’s departure. The audience participated gleefully. The marquesa, absorbed in thoughts of her daughter, noticed nothing and left early, pleased to have gathered material for her next letter.

When the viceroy learned that a member of his court had been publicly insulted, he ordered Camila to apologize in person—motivated by a desire to protect court protocol, maintain good relations with the increasingly powerful Conde in Spain, and assert authority over the actress. The following day, the marquesa was recovering from heavy drinking when Camila arrived. Having genuinely not noticed the insults, the marquesa praised the performance warmly. The actress, interpreting this as extraordinary forgiveness, was overcome with shame. The marquesa then became emotional, recounted a fabricated memory of reconciliation with her daughter, and collapsed.

Around this time, the marquesa borrowed a young orphan girl named Pepita from the Convent of Santa María Rosa de las Rosas to serve as her companion. The convent’s abbess, Madre María del Pilar, had identified Pepita as exceptionally capable and was training her as a successor, sending her to the marquesa’s household as part of this education. However, life with the marquesa was difficult for Pepita. Palace servants stole freely from their employers and played cruel tricks on Pepita. The marquesa would sometimes abandon her for hours in public. Pepita still wore her orphanage uniform, which caused her acute embarrassment. Most painful was the marquesa’s inconsistency—occasionally warm but more often distant.

When the marquesa learned that Clara was pregnant, she was seized with anxiety. She engaged in elaborate superstitious practices, consulted folk healers, performed rituals, and attended numerous early morning Masses. Eventually, she made a pilgrimage with Pepita to the mountain shrine of Santa María de Cluxambuqua. When the marquesa saw the peaceful town set among high peaks, her frantic prayers ceased, and she began to feel a new sense of resignation. A special messenger arrived with letters from Spain. Her son-in-law’s note was affectionate, but Clara’s letter was filled with cutting remarks. The marquesa chose to forgive her daughter before returning to the shrine.

Meanwhile, Pepita attempted to write to the abbess. Lonely and overwhelmed, she composed a desperate letter expressing her isolation and begging for reassurance or permission to return to the convent.

Back at the inn, the marquesa burned her protective charms, declaring that events were beyond her control. She then found and read Pepita’s letter, struck with envy for the simple, devoted love it expressed. At supper, the marquesa offered to enclose Pepita’s letter with her outgoing mail, but Pepita refused and tore it up, explaining only that it was not brave. This statement led the marquesa to recognize that she had never brought courage to her life or relationships. That night she wrote what she called her first letter, a work that became known as Letter LVI, famous for its meditation on love.

At dawn, the marquesa looked at the sleeping Pepita and whispered her determination to begin a new life. Two days later, returning to Lima, the marquesa and Pepita were crossing the bridge of San Luis Rey when it collapsed, killing them both.