Hong Gil-dong (Lee Je-hoon) is a private detective with no fear, no sympathy, no memory, and no friends. He has a 99% success rate in solving cases and can usually find the person he is looking for within a day. However, the only person he cannot catch is Kim Byung-deok (Park Geun-hyung), the murderer of his mother. When the case finally has a clue, it is discovered that Kim Byung-deok has been kidnapped. While tracking his whereabouts, Hong Gil-dong falls into a huge dark organization and discovers the truth about the mysterious organization, the Gwang Eun Society. At the same time, the mysterious man Kang Sung-il (Kim Sung-kyun) has been monitoring Hong Gil-dong's movements...