When Princess Mu Qingyuan's fiancé General Xiao Jingyuan returns victorious with a suspected Northern Di spy Su Wanqing, the victory celebration turns deadly. Su repeatedly oversteps, and Xiao defends her every move. Sensing something wrong, Mu plots with the Emperor to test Su—revealing her assassination plot. Though Xiao realizes Su is suspicious, he's already fallen for her. He pays the price for his divided loyalty while Mu finds new purpose—and an unexpected connection with the Imperial Guard Gu Jinghan—as she navigates the dangerous waters of court politics.
