The Empress's closest officials are dying one after another, and rumors claim that a woman ruling from the throne defies Heaven's mandate. As the Grand Tutor prepares to seize power, four women of the Jishu Bureau—Bai Qing, Li Yue, Qing Lan, and Xiao Man—are ordered to investigate a series of bizarre cases. From an illusion formation in the abandoned palace and mechanisms made of meteoric iron to abducted young girls and smuggled military weapons, they unravel mysteries and defeat powerful enemies at every turn. In the end, they present irrefutable evidence before the imperial court, forcing the Grand Tutor to confess.