During the Lantern Festival, Princess Ningyuan dies mysteriously at the night banquet. Li Peiyi, Princess of Fuchang County, and Xiao Huaijin, deputy director of the Astronomical Bureau, are ordered to investigate. Cold on the outside but kind at heart, Peiyi reads people fast and fights even faster. Huaijin is meticulous, with a razor-sharp memory. Working in sync, they follow threads through arrogant nobles and an Imperial Guard commander hiding secrets, cracking the case and unmasking the killer. More eerie palace mysteries soon follow, each tied to the fates of women in the inner court. As they chase truth deeper into the Tang palace, they also uncover what really happened behind Peiyi's family massacre fifteen years ago, and the mastermind's plot. In the end, Peiyi clears her father's name, finds loyal allies at her side, and earns hard-won redemption.