The story is set in China during the wars between the Jurchen-led Jin Empire and the predominantly ethnic Han Song Empire. Yang Tiexin and Guo Xiaotian, a pair of sworn brothers, pledge that their unborn children will become either sworn siblings (if both are of the same sex) or a married couple (if they are of opposite sexes). One day, Yang Tiexin's wife, Bao Xiruo, saves a wounded Jurchen warrior, who turns out to be Wanyan Honglie, the sixth prince of the Jin Empire. Wanyan Honglie later sends his troops to attack Yang Tiexin and Guo Xiaotian's village. Guo Xiaotian is killed while Yang Tiexin goes missing.