During the Lantern Festival, Princess Huai Si mysteriously dies at a banquet. Li Pei Yi, the chief guard, and Xiao Huai Jin, the Lingtai Lang, are tasked with the investigation, uncovering that the princess was the murderer. Betrayed and wronged, she avenged herself by punishing her betrayer and the daughter of a powerful family before jumping off the Penglai Terrace to escape her marriage fate.

Li Pei Yi and Xiao Huai Jin then uncover a series of strange cases in the inner court, exploring the fate of women in the Tang Dynasty harem. In the process, Li Pei Yi unravels the truth behind a ten-year-old murder and exposes a conspiracy involving the right prime minister and a concubine.