In the final years of the Goguryeo kingdom, a deep unrest stirs within the court. General Yun Gae Soo Moon (Choi Min Soo), a voracious political player, sets his eyes on the throne, forcing King Young Ryu (Kim Young Chul) to hatch an assassination of the would-be military dictator. However, General Yun catches onto the plan and strikes with a bloody execution of the king and his council. Young Princess Moo Young (Kim Ok Bin) survives and vows to exact vengeance on the General one day, eventually becoming a spy who infiltrates his camp. However, the princess falters when she falls in love with Yun Choong (Uhm Tae Woong), the general's illegitimate son, who will do anything to be acknowledged by his distant father.