In the early Republic of China, Qian Yiyu, the adopted daughter of Qian Fan, the old butler of the wealthy Liu family—grew up as childhood sweethearts with Liu Sinan, the second young master, and the two were engaged to be married. However, on the night of their wedding, she was suddenly forced to marry Liu Silin, Liu Sinan’s deranged elder brother. Resentful toward the man who took the place of her beloved, Yiyu must still pretend everything is fine; for she has a secret mission: to help Liu Sinan spy on his brother.It turns out that the elder brother’s downfall was orchestrated by Liu Sinan himself, who seeks to seize the entire family fortune. Yet, despite Yiyu’s hostility and defiance, Liu Silin treats her with patience and tenderness. As Yiyu continues to watch over him, she is gradually moved by his kindness, and love quietly blossoms between them. But their fragile affection is constantly tested by manipulation and deceit; eventually uncovering the shocking truth behind the murder of Yiyu’s biological parents.