To escape a life of poverty, Hwa-yeon (Cho Yeo-jeong) becomes a royal concubine to King Gwang-hae, forcing her to abandon her true love, Kwon-yoo (Kim Min-jun). Years later, when the King dies, his weak stepbrother Sung-won (Kim Dong-wook) takes the throne under the brutal manipulation of the Queen Mother, sparking a chaotic palace power struggle. Driven by a long-standing, obsessive lust for Hwa-yeon, the new King appoints a castrated Kwon-yoo as a palace eunuch, trapping all three in a claustrophobic, violent web of sexual betrayal, political assassination, and brutal revenge as Hwa-yeon transforms into a cold strategist to protect her young son from the deadly court executioners.