When a brilliant but trigger-happy detective is outsmarted by a serial killer, he pays a high price for his momentary lapse in judgment. Robbed of both his fiance and his job, he soon spirals out of control and goes back to what he knows best: fighting. Unbeknownst to him, a serendipitous reunion with an old rival may be the key to unlocking the truth about his fiance's disappearance, and to apprehending the killer.

Forensic psychologist Mu discovers invisible clues at the scenes of elaborate vigilante murders. The murderer is plotting his most disgusting act yet; live streaming an execution where the people decide the victim's fate. But as Mu closes in on the killer, he remains unaware that the murderer's true motives lie in Mu's past.