Set in the year 1258 during the Goryeo Dynasty, as some thirty years of war with the Mongols near defeat, an expedition of hope, led by the young and passionate warrior Baek Gyul, embarks on a perilous mission to recover a sacred jewel believed to hold miraculous powers to protect the nation. Breaking through enemy lines, they journey beyond the mountains toward the eastern sea, with the help of Princess Wang Hee, who races to their aid.