Shen Wu, daughter of the General Who Guards the North, is forced to enter the imperial palace as a hostage. Naturally suspicious to an extreme, she lives by one belief: "Someone is always trying to harm me." She secretly wears a protective chest mirror even when summoned to the emperor's bedchamber and has the imperial trees chopped down to prevent assassins from hiding among them. Little does she know that her constant vigilance will accidentally expose traitors colluding with the enemy and solve a series of mysterious cases in the imperial harem! Concealing her medical skills, she saves the Empress Dowager and protects the imperial heir, then turns the tables to bring down the treacherous Empress and the powerful corrupt chancellor. From a hostage constantly walking on thin ice to the Empress of the Empire, Shen Wu uses her formidable abilities to reform the imperial court. Finally, when enemy forces threaten the borders, she joins the emperor on the battlefield to defend their vast empire together.