The fourth prince Xiao Xian was about to lie down and enjoy life. Unexpectedly, the emperor's father granted a marriage to Su Wan, the daughter of Su Lie, the king of Zhenbei, the guard of Yanmen Pass. However, the king of Zhenbei did not listen to the announcement. Why did he agree to this marriage? More than ten years ago, the queen secretly sent people to kidnap and kill the southern barbarian chief. The southern barbarians rebelled and the southern barbarian princess who competed with the queen was given death. The emperor sent the princess' son to the king of northern Xinjiang. Was it exile or protection?