Wilhelm returns with Felix and meets Lothario, who has resumed control of the estate business with clarity and purpose. Wilhelm, however, is inwardly troubled, knowing that Lothario is Theresa’s rightful suitor. During discussions, Lothario reflects on property and justice, arguing that land ownership should contribute fairly to the state. The negotiations proceed, and Lothario soon sends Wilhelm on an urgent journey to his sister, where Mignon’s health is said to be “decaying more and more” (457). Wilhelm departs in deep anxiety, fearing a painful reunion with the countess. On the road, he realizes that the note summoning him isn’t from her but from “his Amazon,” the mysterious woman who once saved him. Realizing that she is Lothario’s other sister, Natalia, he continues with renewed hope.

Upon arrival, Wilhelm enters a grand house filled with familiar artworks. He recognizes his grandfather’s art collection, which his father sold to finance his business ventures. Overwhelmed, he kneels before Natalia. She receives him calmly and explains Mignon’s fragile condition, describing her physical and emotional decline. Natalia also recounts how Mignon began to wear feminine clothing after being dressed as an angel for a symbolic performance. Wilhelm is deeply moved, uncertain of Natalia’s situation and restless with anticipation.

Wilhelm settles into Natalia’s house and explores its art, library, and collections but is troubled by his unanswered proposal to Theresa and by concern for Mignon. At breakfast, he learns that the portrait above the sofa is not of Natalia but of her aunt, the “fair saint” whose manuscript he read to Aurelia.

Natalia and Wilhelm discuss the abbé’s ideas on education, especially his belief that upbringing should follow natural inclinations. The doctor then explains what he has pieced together about Mignon’s history. She was abducted in childhood from the region near Milan and vowed never to reveal her origins after being betrayed by those who found her. He also reveals that her love for Wilhelm became painfully intense, especially after she witnessed another woman entering his room at night. Wilhelm’s presence now calms her somewhat.

Natalia reveals that she already knows that Wilhelm has proposed to Theresa and gives him Theresa’s acceptance letter. Theresa offers him marriage based on practical harmony and mutual esteem, and Natalia shares further letters in which Theresa explains why she believes Wilhelm suits her better than Lothario. Wilhelm is shaken, however, upon recognizing his growing attachment to Natalia. Their discussion is interrupted when Jarno arrives with startling news: Theresa is allegedly not the true daughter of her reputed mother, and this removes the barrier to a marriage between Theresa and Lothario. Wilhelm immediately offers to renounce Theresa for Lothario’s sake. Yet new letters from both Theresa and Lothario deepen the confusion; Theresa still plans to marry Lothario, and Lothario is content to wait for her to fully believe the news. Amid his “great disquiet,” Natalia persuades Wilhelm to stay and wait. She declares that love has always seemed to her “a fable.”

As they talk, Wilhelm and Natalia explore a lavish tomb, the Hall of the Past, constructed on the family estate. The tomb features a space for a hidden choir. Their conversation is interrupted by Mignon chasing Felix. Natalia chides the young girl, who has been “forbidden violent motions” (486). Mignon brings news that Theresa has arrived. Theresa enters just as Mignon collapses “as dead.” Doctors are summoned amid Wilhelm and the others’ shock. Upon seeing the doctor, Wilhelm again recognizes his travel bag and learns that it belonged to the doctor’s father, who treated his wounds after the bandit attack. Lothario, Jarno, and the abbé arrive as the characters mourn Mignon’s death.

Jarno explains the origin of the Tower Society. It began as a youthful association devoted to secrecy, art, and self-cultivation, but under the abbé’s influence, it turned toward practical observation of character and life. Jarno reads parts of Wilhelm’s “indenture” and defends the society’s efforts to watch, guide, and test him. Jarno says that the abbé values every human gift and believes that each person must be developed according to natural capacities. Revealing that it was either the abbé or his brother who played the Ghost, he repeats his view that Wilhelm has no true vocation for the stage. He urges Wilhelm to stop focusing on himself and consider the larger world. When the abbé appears walking with Natalia and Theresa, Jarno hints that he’s already “contriving something.”

The abbé explains that Theresa isn’t the daughter of the woman who raised her. Because Frau von C. had repeatedly borne stillborn children and had been warned that another pregnancy would kill her, she and her husband agreed to pass off the child of his mistress, the household manager, as her own. The real mother consented, Theresa was presented as the lawful daughter, and the mistress died soon after childbirth. Frau von C. gained the social advantage of motherhood and removed her rival, though Theresa’s father later tried, unsuccessfully, to reveal the truth before his death. The abbé produces papers proving the story and admits that Lydia’s suspicions were partly justified since he had long hoped for a union between Theresa and Lothario. Wilhelm resolves at once to renounce Theresa and asks only for a formal release, but Jarno delays any final settlement, and the matter remains outwardly unresolved.

Jarno announces that he plans to sail to America as part of a broader scheme formed by the Tower Society to secure members against political upheaval by spreading trusted allies across different countries. He offers Wilhelm the choice of joining him abroad or remaining in Germany with Lothario and advancing the society’s interests there. Friedrich (now returned and revealed to be Lothario’s brother) jokingly proposes that he and Wilhelm should each take a woman with them, suggesting “the fair, soft-hearted” Lydia (504), but Jarno reveals that he himself has already offered Lydia marriage. Soon after, the abbé introduces another plan: The marchese, an Italian nobleman and old friend of Lothario’s uncle, needs a learned traveling companion through Germany, and the abbé proposes Wilhelm. Wilhelm resents what he sees as another attempt to dispose of him. Left alone, he admits to himself that he loves Natalia and suffers at the thought of leaving her. He reflects on the various women whom he has loved, his love for his son, and his “piercing grief” at the loss of Mignon. When the marchese arrives, Wilhelm feels detached from the conversations about art.

The abbé leads the company to Mignon’s funeral in the Hall of the Past, which is richly decorated and illuminated. Her embalmed body lies on the sarcophagus in her angelic dress, while boys and an unseen chorus perform a solemn musical rite that lays Mignon to rest and urges the living to return to life. The abbé speaks briefly of her unknown origins, her deep attachment to Wilhelm, and her early death. When her arm is revealed, marked with a crucifix, the marchese recognizes her as his long-lost niece, believed dead after being abducted in childhood. The body is then sealed in the coffin, and the ceremony ends in silence and deep emotion.

The marchese avoids further discussion of Mignon but prepares to depart, inviting Wilhelm and the others to visit her homeland and learn her history. The countess arrives, and the abbé reads a written account from the marchese explaining Mignon’s origin: A noble family’s hidden daughter, Sperata, unknowingly fell in love with her own brother, Augustin. When the truth was revealed, Augustin refused to accept it and descended into turmoil, while Sperata was separated from him and driven to religious despair. Their child, Mignon, was raised elsewhere, showing unusual traits and restlessness, but she was eventually lost and presumed drowned. In her guilt and grief, Sperata died believing in her child’s resurrection. Augustin later escaped his confinement in a monastery and disappeared, with his family presuming that he had taken his beloved harp and “gone to Germany” (528).

The characters surmise that the harper, now recovered, must be the marchese’s lost brother. The marchese, thankful to Wilhelm for caring for Mignon, invites Wilhelm to accompany him on a journey and to bring Felix. When the harper is brought back to the castle, a tragedy nearly occurs when Felix seemingly ingests the laudanum that the harper now carries with him to remind him of the value of life. Falsely believing that Felix is dying, the harper (Augustin) dies by suicide. Felix is saved by his own “naughtiness,” having drunk from the bottle rather than the harper’s cup, which contained the laudanum.

The abbé reveals that Theresa agreed to marry Lothario on the condition that Natalia should marry Wilhelm. Friedrich’s eavesdropping exposes Natalia’s resolution that she would offer herself to Wilhelm if Felix survived. Lothario then explains that he and Theresa had already recognized Wilhelm’s attachment to Natalia and had silently allowed events to reach their proper conclusion. He asks Wilhelm to remain, join their circle, and work with them in a life of useful action rather than restless wandering. Natalia and Wilhelm are finally united (though Wilhelm will first travel to Italy with the marchese), while Theresa and Lothario are paired together. Friedrich jokes that Wilhelm, like Saul, set out on a small errand and unexpectedly found a kingdom. Wilhelm answers that he has found a happiness beyond anything he deserved and would “not change with anything in life” (542).