In Republican-era China, orphan Lin Chuning believes her best friend Xiaorou was killed by the wealthy playboy Lu Siyan. Bent on revenge, she infiltrates the Lu family by impersonating his long-lost "twin sister," posing as the missing heiress to get close to him and exact vengeance.

The cool woman has to play a maid who has always been humiliated while the gentle CEO has to pretend like he's a brutal prince. She sharpens her dagger every night, trying crazily to kill him; He teases her every day, trying desperately to win her heart. In this amusing and romantic love duel, let's see who can gain ground and complete the mission first. During the duel, they begin to realize that they're caught in a conspiracy.