King junmyeon and his brother yunho has made a deal that yunho's son will be the next king because junmyeon's wife jisoo can't be pregnant, so junmyeon was really happy that his brothers child sehun will be the next king but when sehun was two year old king junmyeon's wife was announced as pregnant, sehun's mother yoona felt betrayed when everyone in the kingdom started calling junmyeon's new born son the next king, she has planned to kill the king and his son, but when the day the king and queen were attacked no on saw a sign of the king's new born son, everyone thought he died, after several years when sehun should be the king but people still think the real prince is alive, so yoona asked her son sehun to search for the prince and kill him.