Mongolian Empire, 14th Century. Two horse-riding children, Alexandria (Aleks), and her brother Yury, travel to the Great Wall of China for the first time. Although their father warns them to keep away, they disobey him and become friends with the young people on the other side of the wall. In this strange land they learn to their horror that their peaceful existence is about to be shattered. War between the two countries seems inevitable. There has been a history of fighting, but what can young people do to stop it in an adult world?