During the Shangyuan Festival, Princess Ningyuan dies mysteriously at a night banquet. Li Peiyi, County Princess of Fuchang, and Xiao Huaijin, Deputy Director of the Astronomical Bureau, are ordered to investigate. A peerless fighter who is also skilled at reading people, Li Peiyi is cool-headed but kind-hearted, and single-mindedly pursues the truth. Working in perfect accord with Xiao Huaijin, whose thinking is meticulous and memory exceptional, she follows the clues piece by piece. Through an arrogant noblewoman and a Jinwu Guard officer with secrets of his own, they eventually uncover the truth and identify the culprit. The pair then join forces to solve a series of tangled palace intrigues within the inner court of the Tang dynasty, as one bizarre case follows another. In cases that reveal the fates of all manner of women in the imperial harem, Li Peiyi and Xiao Huaijin explore the wonders of the Tang dynasty and experience the strange passions of the human world. As they solve these crimes, they gradually uncover the truth behind the massacre that wiped out the Li family fifteen years ago, ultimately exposing the mastermind's plot. Li Peiyi not only clears her father of the false accusations against him, but also gains companions who stand by her as she pursues the truth. Together, they build a deep bond and help each other find redemption.