During the Lantern Festival, Princess Huaisi died mysteriously at a night banquet. Xue Peiyi, the chief guard of the inner court, and Gu Heng, the Lingtai Lang of the Taishi Bureau, were ordered to investigate. Through the domineering daughter of a powerful man and the secret-bearing Jinwu guard Yu Linlang, they finally found out.Find out the truth and find the real murderer.Subsequently, a series of intricate "Secret History of the Palace" and strange cases that occurred in the inner court of the Tang Dynasty followed one after another.In one case after another involving the fate of various women in the harem, Xue and Gu explored the wonders of the Tang Dynasty and felt the wonders of the world. In the process of solving the case, they gradually found out the truth behind the Xue family's murder case ten years ago, and finallyReveal the conspiracy behind the scenes.Xue Peiyi not only cleared the grievances of her father, General Xue, but also established a deep relationship with Gu Heng in the process of pursuing the truth, a story of mutual redemption.​

Through complex cases and character relationships, this drama shows the good and evil of human nature, love and hatred, and conveys the persistence of justice and truth.