Set in an unnamed, declining European city where nature is slowly overtaking civilization, the novel is narrated by Agathe, a young woman who describes herself as emotionally numb, with a dead rock at the center of her soul. The morning after her mother's suicide attempt, her uncle, a frail former literary critic with whom she lives, advises her that writing in the first person is the safest disguise. Agathe takes his advice, though what she writes about is not her mother but her boss and the events of the summer that followed.
Agathe has spent four years doing almost all the academic work for her boss, a wealthy foreign woman who lectures in city planning at the local university. Hired ostensibly to tutor the boss's son, referred to as "the child," Agathe writes lectures, marks papers, and composes emails. The boss, from a rising southern city and married to a famous architect named Richard, is deeply insecure and subjects Agathe to interminable monologues about her loneliness. Despite the boss's incompetence, her course has grown popular, largely because of Agathe's hidden contributions.
The central crisis arrives when Adam, a charismatic student from the boss's home city, clashes with Jacob, a young professor whose ancestors were once enslaved and later subjugated by the city's dominant population. During a seminar, Jacob dismisses Adam's argument as conspiracy theorizing; Adam retorts with a remark about how things are done "wherever Jacob was from." Each reads the other's words as a culturally loaded insult, given their communities' respective histories of persecution and subjugation. Jacob lodges a formal complaint, and the administration transfers Adam without explanation. The boss defends Adam passionately, accusing the city's inhabitants of dissecting every situation until they prove the presence of evil.
Agathe and her uncle visit her parents. Her mother's attempt to drown herself in the bath has left her with irreversible brain damage. Agathe's father, a famous writer and editor, addresses his unresponsive wife in a monologue, characterizing Agathe as a stranger who was "born badly" and confessing that he and his wife united against their daughter. He begs the mother to raise her hand in reconciliation, but she remains motionless. Watching gardeners on the lawn, Agathe enters a visionary state. She hears gardeners tell of a woman who falls in love with her killer in a recurring dream, debating whether love is the capacity to endure eternal murder.
When Adam visits the boss's house, Agathe, whose existence must remain secret from students, hides upstairs and eavesdrops. The boss then sends Agathe to befriend Adam at the university and report on his state of mind. Agathe finds him in the library and improvises a cover story: She tells him she is researching mercy and forgiveness for an unnamed academic. Startled by his beauty and intensity, she begins meeting him daily. Their conversations are intellectual and guarded, and Agathe reports only abstract exchanges to her frustrated boss. Meanwhile, Agathe's father demands she take her mother on weekly walks. Since her mother cannot move, Agathe climbs into the wheelchair on her mother's lap, operates the lever, and they glide through the overgrown neighborhood.
When speaking to Adam, Agathe disguises her boss as her mother and her actual mother as the anonymous academic. Through these reversals she expresses feelings she has never articulated: hatred for the boss's narcissism and tenderness for her damaged mother. Adam shares his own loneliness and his sense that no one sees past his surface. One day, Agathe's father encounters them on campus and confesses that every one of his novels has been an attempt to capture Agathe's character and that every attempt has failed. Shortly afterward, gardeners shovel dirt into the college's historic fountain in a symbolic act of defiance. During this scene, Adam takes Agathe's hand. She does not pull away, but the gesture obsesses and disturbs her.
Adam, the son of two architects who never fully belonged to either his home city or Agathe's, declares his ambition to change the city through architecture. When Agathe insists nothing matters, Adam calls her ungrateful and walks away. She has an erotic dream about him and resolves to stop seeing him but finds herself back at the university, where she sees Adam talking with her father and flees.
Agathe withdraws from everyone. The schoolmaster, her uncle's friend, visits to announce he has been fired. He reports seeing Jacob meeting with the gardeners in the botanical gardens, though he could not hear their conversation through the glass separating them. Based solely on this observation, he speculates that Jacob and the gardeners have conspired to restructure the relationship between the university and the city. Jacob has been promoted; Adam will likely be expelled.
Agathe travels on foot to her father's house. Her father delivers a speech alluding to a traumatic incident from her childhood involving a staircase. He implies that something happened, that it led him to remove all the staircases from the house, and that they were told she would not remember. He says she was never forgiven. Agathe cannot determine whether this is truth or fiction. She walks into the park and wanders for hours in darkness.
She arrives home to find Adam on her bed; her uncle has let him in. Agathe confesses everything: She was sent by the boss to spy on him, she overheard his conversation at the boss's house, and she finds him boring. Adam says he does not believe her and that she has come to mean something to him. They sleep together. Afterward, Adam tells her about a painting of the Annunciation that inspired him to become an architect: a cramped room where a table separates Mary from the angel and the windows suggest no escape. He reveals he will be suspended and possibly expelled. When Agathe's immediate concern is for her own job, he accuses her of never seeing him as human and leaves.
The next morning, a stranger among her uncle's friends tells what he calls the greatest love story of all time: A woman who has always lived in a tower watches as a prince climbs it. She follows his ascent from inside, always staying ahead, never reaching out. When the prince reaches the roof, he steps through a glass dome and falls to his death. The woman realizes she never extended her hand. The schoolmaster notices that Agathe is crying.
Agathe goes to the boss's house and quits. The child confronts her, calling her selfish and a monster, but gives her his number. Outside, Richard has just returned. He tells Agathe that the university and the gardeners have reached an agreement: The gardeners will restore order, and the university will expand with a new campus Richard has been commissioned to build. Yet Richard dreams of something grander, an "angelic city" beneath a glass dome, with an emptiness at its center that he identifies as God.
The final chapter opens with Agathe directly addressing Adam, revealing she has been writing this book for him. She loads her unresponsive mother into a wheelbarrow, pushes her to an ornamental pond, and tips her into the water. The boss's gardener finds her and shows her an orangery, a glass conservatory he has rebuilt using panes from the boss's property. He says it will not last, but he built it for the beauty of individual moments. Alone in the orangery, Agathe envisions Adam and tells him a story: A village loves a white whale that brings them prosperity, but the whale vanishes. When a dead white whale washes ashore, the villagers choose to believe it is a different whale and continue to wait. Agathe sees herself clearly for the first time and sees Adam clearly too. She extends her hand. He takes it.