Set during the early Joseon Dynasty, the film begins with the queen mother and former concubine (Park Ji-young) in a precarious position of having no blood ties to the childless king (Jung Chan). She schemes to replace him on the throne with his stepbrother and her submissive young son Sung-won (Kim Dong-wook). Indifferent to his mother’s plans, the timid prince falls in love at first sight with Hwa-yeon (Jo Yeo-jeong), an aristocrat’s daughter, who has already found love with Kwon-yoo (Kim Min-joon), a low-born commoner. When her father (Ahn Suk-hwan) decides to send her to the royal palace as a concubine, the two lovers try to elope but are caught after their first night together. She only gives in to parental demands in a quid pro quo for his life. Five years later, Hwa-yeon has become the queen after producing a male heir. This infuriates the queen mother and breaks the hearts of both Prince Sung-won and Kwon-yoo, who later joins the royal palace as a eunuch for the queen mother's brother and nemesis. The king is eventually poisoned to death by the queen mother, who is desperate to be in power. She sits her son, Prince Sung-won, on the throne as a puppet king, giving the ruthless matriarch firm control over the royal court. Hwa-yeon is moved to a closely watched humble residence, with the queen mother planning to assassinate Hwa-yeon and her son to secure her position in the palace. Upon finding out she and her son are in danger, Hwa-yeon gradually becomes monstrously ambitious, using everyone around her, including her castrated former lover Kwon-yoo and now-King Sung-won - as tools for her own survival.