During the Tianqi period of the Ming dynasty, factional disputes in the court are rife and eunuchs hold much power. Late one night, Cui Si, a member of the eunuch party, dies suddenly and mysteriously in his residence. Wei Zhongxian is furious and orders the Imperial Guards to investigate the matter thoroughly, and military official Xu Panxing appoints Chu Mo of the Imperial Guards to supervise the case. Despite his strong sense of justice and reluctance to get involved with the eunuchs, Chu Mo has no choice but to accept it. However, as the case deepens, a huge conspiracy is gradually revealed.