To avenge herself, Shen Jingxian, a female assassin from Nanli, attempts to assassinate Pei Jin, the tyrannical emperor of the Yan Kingdom, at a peace negotiation banquet. Unexpectedly, the two touch the Mirror of Mountains and Rivers, causing their souls to switch bodies. The assassin finds herself inhabiting the emperor's body, while the tyrant is trapped in a woman's body. Forced to impersonate each other, they must navigate a palace full of hidden dangers. With the Empress Dowager urging the emperor to choose consorts and Nanli sending over male attendants, the two join forces to resolve one farcical crisis after another, gradually letting go of their suspicions. They discover that their body swap was a plot orchestrated by the Imperial Preceptor, Xie Wugou. The way to reverse it is to transfer their souls with a kiss, but the Mirror of Mountains and Rivers is destroyed soon afterward. The two are also poisoned with the Qianji toxin, linking their pain and lives together. To unravel the conspiracy and find a way to return to their original bodies, the pair whose fates are now intertwined must venture together to Soulbreak Cliff and confront the mastermind behind it all.