Hong Jitong (Li Dixun) is a private investigator who has no fear, no compassion, no memory and no friends. The success rate of entrusting the incident is as high as 99%, and the person he is looking for can usually be found in no more than a day. However, the only thing he can't catch is Kim Byung-tak (Park Genkun), who killed his mother. When there was finally a clue to the case, it was found that Kim Bingde had been kidnapped. Hong Jitong fell into a huge dark organization while tracking his whereabouts, and discovered the truth of the mysterious organization, the Society of Light. At the same time, the mysterious man Jiang Chengri (Kim Sung-Jun) has been monitoring Hong Jitong's movements.