During the tumultuous Ming Dynasty, four young detective guards who each excel in a different form of martial arts, fight corruption and maintain justice in the land. "Cold Blood" is Leng Xie (Hans Zhang), a master swordsman. "Heartless" is Wu Qing (Yang Yang), a specialist in using hidden weapons. "Chaser" is Zhui Ming (William Wai-Ting Chan), an expert at Qing Gong. "Iron Fist" is Tie Shou (Zijun Mao), a master boxer. Their teacher, sheriff Zhu-Ge Zhen-Wo (Howie Huang), also takes in Chu Li-Mo (Janine Chun-Ning Chang) after she is saved by Leng Xie while escaping the palace, and she develops her talent for mindreading.