During the Lantern Festival, Princess Ningyuan dies under mysterious circumstances at a palace banquet. Li Peiyi, Princess of Fuchang County, and Xiao Huaijin, deputy director of the Astronomical Bureau, are tasked with the investigation. Sharp-eyed and formidable in combat, Peiyi pairs with the meticulous and brilliant Huaijin to uncover the truth. Their search leads them through treacherous nobles and an Imperial Guard commander hiding dangerous secrets. As more unsettling palace cases emerge—each tied to the suffering of women in the inner court—the conspiracy deepens. Tracing the clues back fifteen years, Peiyi confronts the truth behind her family’s massacre and the mastermind pulling the strings. In the end, she clears her father’s name, gains steadfast allies, and earns hard-won redemption.