Lu Zhiqheng, the third young lady of the General's Mansion, searches for her missing father and brothers, but unexpectedly saves a girl possessed of the Lu family's purple pupil anomaly. Looking at the girl before her who likewise has purple pupils, Lu Zhiqheng suspects that her younger sister Lu Zhiyuan in the mansion is an impostor. After returning to the mansion and probing her through a series of tests, Lu Zhiqheng's suspicions deepen; she feigns wanting to kill the fake sister, discovers she lacks purple pupils, and grows suspicious of her stepmother and the imperial concubine aunt who previously raised the fake sister. While toying with everyone, Lu Zhiqheng searches for evidence. Ultimately discovering the imperial aunt's heaven-shaking conspiracy, in the process of exposing the truth, Lu Zhiqheng finds that the matter is far from as simple as she had imagined!