The year is 927. After the prince of Balhae was assassinated, Lim, a former official, sends Yeon So-ha, a female warrior to escort Prince Dae Jeong-hyun from his 14-year exile back to Balhae, where he would ascend to the throne and restore order to the kingdom. The pair, however, find the journey to Balhae a perilous one. In this epic struggle of good and evil, the fate of a nation hangs in balance.