The narrative begins with the whispers of high society regarding the engagement of Rebecca Laruelle to Charles, the Duke of Valerian. Rebecca is widely rumored to be a "witch," a woman of extravagant tastes, arrogance, and a scandalous reputation for ensnaring men. The Duke, known as "Frozen Blood," is a feared judge, notorious for his cruel and emotionless rulings, and rumored to be a sadist who drives his female staff to tears. Despite his fearsome reputation and striking, almost intimidating beauty, the engagement is presented as a divine match, a "witch" for a man who seems to embody coldness. Rebecca's mother laments her daughter's upbringing, contrasting her with her virtuous and pure younger half-sister, Emily, who is a candidate for sainthood. Emily, a stark contrast to Rebecca's perceived wildness, is depicted as a model of purity and grace.
The story then flashes back several months to reveal Rebecca's true circumstances. She lives in her family's opulent mansion but is relegated to the north wing, treated more like an animal than a daughter. Her stepmother, after Rebecca's mother's death, favors Emily, showering her with affection and gifts while Rebecca is told to endure and even has her belongings taken. Her father is distant and seemingly influenced by his new wife. Rebecca survives due to the quiet kindness of a few long-serving maids, particularly Sarah, who risks punishment to provide her with food and necessities. Crucially, Rebecca lacks magic, a rare trait in this world, making her an anomaly and contributing to her ostracization.
The stepmother's cruelty escalates when Emily discovers she has magic, fueling her favoritism and the plan to make Emily a saint. Rebecca is deliberately dressed in gaudy, outdated clothes and made up heavily, leading to her being labeled a "witch" and a woman of loose morals. Emily, driven by jealousy of Rebecca's natural beauty and grace, cruelly mocks her, finding pleasure in Rebecca's social humiliation. Isolated and despairing, Rebecca finds solace in a hidden box of books about plants. This discovery leads her to venture outside the forbidden north wing and connect with the natural world, finding peace in the wildflowers.
On her eighteenth birthday, the age of adulthood, Rebecca resolves to leave her oppressive home and become a florist or botanical garden attendant. Her father, however, summons her, revealing the engagement to Duke Valerian, a prospect that terrifies her due to his notorious reputation. Her stepmother and Emily react with a mixture of disdain and morbid curiosity, mocking her potential fate. Her father offers no support, leaving Rebecca feeling utterly alone.
Three days later, a letter arrives from the Duke's household, rejecting the marriage proposal. The stepmother is enraged, viewing it as an insult. She forces Rebecca, dressed in revealing attire and heavily made up, to go to the Duke's mansion to "entice" him, intending to use Rebecca's supposed "witchy" nature to her advantage and later claim Rebecca coerced her. Left at the imposing gates in the cold, Rebecca encounters a unique blue Rosetta flower, broken but beautiful. She attempts a crude graft using a piece of her dress, a small act of preservation. The Duke, Charles, emerges, his striking beauty and piercing gaze intimidating Rebecca. She explains her predicament, stating she was abandoned by her stepmother. Charles, initially dismissive, seems intrigued by her plea for shelter, even if it's just in a stable.
Inside the Duke's mansion, Rebecca is treated with surprising kindness by the staff, who provide her with warm tea and comfortable lodgings. The Duke, meanwhile, discusses Rebecca with his trusted servants. They debate whether she is truly the "witch" of rumor, noting her apparent lack of magic and her attempt to conceal her figure. Charles confirms her identity, recalling seeing her at a party where she was nearly harmed. The servants express concern for his safety, given his reputation. Charles, aware of the dangerous rumors surrounding him, including accusations of sadism, finds Rebecca's visit peculiar. He learns she attempted to graft a broken flower, hinting at her interest in plants.
The Duke's staff proposes a plan: a temporary, written engagement to prevent Rebecca from fleeing to commoner status and to avoid repercussions from the Laruelle family. This would allow the Duke to eventually break the engagement without consequence. Meanwhile, at the Laruelle estate, the stepmother is furious about the lack of a dowry for Rebecca's marriage, as the Duke intends to support Rebecca himself and forgo traditional wedding celebrations. She prioritizes Emily's saint candidacy, lamenting the financial strain.
Rebecca, unaware of these machinations, begins to adapt to her new life in the Duke's mansion. She finds joy in the spacious gardens, tending to the Rosetta flowers and learning from a skilled gardener named Leo. Her days are filled with plant research and gardening, a stark contrast to her previous life. Her maid, Elaine, constantly tries to dress her in more appropriate, luxurious attire befitting a future Duchess, much to Rebecca's discomfort. The Duke, Charles, finds his work significantly easier now that his engagement is public, as it deters unwanted attention and potential threats. He appreciates Rebecca's presence, which has brought him a sense of peace and allowed him to pursue his own quiet interests. He decides to take Rebecca on an outing, seeing it as a way to show his gratitude and prevent her from feeling too confined.