Shen Zhiyi enters the Marquis's Mansion as a body double, subjected to all sorts of humiliation by the head wife and her legitimate sister. Because her appearance closely resembles Liu Ruyan, the sweetheart of Xie Linyuan, she becomes deeply trapped in the whirlpool of inner courtyard infighting. Step by step, she cautiously investigates the truth behind her mother's imprisonment. Moving from mutual probing and suspicion with Xie Linyuan to jointly breaking through a dead-end scheme, they unearth a shocking major case involving the Liu family colluding with the Northern Frontier and illegally trafficking military arms in an attempt to rebel. After going through life-and-death trials and having her wrongs redressed, the two transition from utilization and confrontation to ultimately becoming soulmates who understand each other's hearts.