The story begins with Sphere Lark, the protagonist, experiencing a sudden and brutal annulment of her engagement to Prince Wagner. Wagner declares her too "gloomy" for royalty and announces his engagement to Aries, her cousin. Aries, who was adopted by the Lark ducal family after her parents' death, claims to love Wagner and believes their previous engagement was merely political, thus justifying her actions. Sphere's father, Duke Atri, who favors Aries over his own daughter, has already granted his permission for this arrangement, believing Aries is more suitable.
Sphere's life has been one of constant emotional suppression to avoid abuse, a consequence of her mother's marriage to her father, who seemingly resented his wife for using her status to marry him. Now, with her engagement broken and no family support, Sphere is ostracized as a "damaged goods" and an "leftover." Unexpectedly, the wealthy Viscount Kimberley proposes marriage to Sphere, a proposal her father eagerly accepts, viewing it as a way for Sphere to be useful. The groom is Dahar Kimberley, a twenty-six-year-old illegitimate son.
Sphere's marriage to Dahar quickly descends into a nightmare. He subjects her to severe physical and psychological abuse, constantly accusing her of looking at others and demanding absolute devotion. He isolates her, allowing her only to eat with him and punishing her for any perceived transgression. His declarations of love are laced with threats, and his jealousy leads to horrific violence. When a gardener offers Sphere a flower, Dahar brutally murders the gardener before her eyes, then turns his sword on Sphere, stabbing her repeatedly until she dies.
Sphere awakens to find herself back in her father's study, holding a quill, with a document before her to make Aries the adopted daughter of the Lark family. The date on the document is seven years prior, indicating she has been sent back in time to when she was sixteen. She realizes she is alive and has a chance to change her fate. When her father demands she sign, Sphere refuses, having no desire to relive her abusive past. Her father reacts with violence, beating her with a cane and accusing her of lacking compassion for Aries. Sphere, however, recalls her own suffering, her unanswered pleas for help, and her lonely death.
Sphere confronts her father, revealing her newfound defiance. He orders her confined to her room. From her window, she overhears Wagner and Aries plotting, with Wagner expressing his disdain for Sphere and his intention to break their engagement and marry Aries once she becomes a duchess. Sphere realizes her previous life was one of manipulation and exploitation. She vows to use this second chance to her advantage, starting by ensuring her engagement to Wagner is irrevocably broken.
At a ball, Wagner publicly slaps Sphere and accuses her of bullying Aries, based on Aries's false testimony. Aries feigns innocence, further manipulating the situation. Sphere, no longer the submissive woman she once was, retaliates by exposing Aries's lies and her own extravagant spending, funded by her father's likely embezzlement. Wagner, enraged, cuts Sphere's hair as punishment, officially breaking their engagement and declaring his intention to marry Aries. Sphere, however, has not signed the adoption papers for Aries, a fact that will complicate Aries's plans.
Later, Sphere learns from her grandfather's spy, Gilmer, that her father has indeed been embezzling funds. She also discovers that Aries's parents died in debt, and the Lark family is burdened with their loans. Prince Weiss, who was previously abroad, visits Sphere, apologizing for Wagner's behavior and offering his support. He confesses his long-held feelings for her and proposes marriage, which Sphere tentatively accepts as a strategic alliance.
Sphere's father and Aries confront her, demanding she sign the adoption papers. Sphere refuses, asserting her right as the true heir and revealing her father's embezzlement and Aries's parents' debts. She declares she will not be manipulated any longer, embracing her new strength and determination to survive and reclaim her rightful place.
