It tells the story of the free-spirited ranger Yun Zhan and his master who were implicated in a bizarre case. They were unexpectedly suspected of being the murderer by Princess Shi Qiuting and bodyguard An Xuewu. In the process of proving his innocence, Yun Zhan gradually found the direction of his life, and teamed up with Shi Qiuting to solve the strange case. Since then, he has shouldered his own mission and responsibility to protect the safety of the people in the imperial city.