A mysterious tragedy strikes when a man's car is struck by an unknown assailant, leading to his death as he steps out to photograph the damage for an insurance claim. In the midst of this chaos, Jung Tae-Suk, portrayed by Mu-Yeol Kim, an upstanding police officer, investigates the scene and suspects foul play from a potential serial killer, yet his superior dismisses his concerns. Simultaneously, gangster Jang Dong-Soo, played by Dong-seok Ma, is returning home from a tense meeting with a rival gang leader about territorial disputes when a violent encounter with the killer occurs, leaving both him and the assailant injured.
As Dong-Soo is hospitalized, his loyal henchmen misconstrue the chaos as a move by a rival gang, prompting them to retaliate. However, Dong-Soo discerns that the attack was not orchestrated by his rivals—there's a more dangerous player involved. When Tae-Suk visits him, pleading for cooperation to apprehend the murderer, Dong-Soo refuses. He instead sends out his men to hunt the killer using a sketch and they soon find a car and a knife tied to a recent murder. Realizing the necessity of collaboration, Dong-Soo reaches out to Tae-Suk and agrees to join forces to stop the killer, motivated by the need to preserve his image and protect his business interests.
The stakes rise as Dong-Soo insists that whoever captures the killer first should have the right to deal with him. While Dong-Soo seeks vengeance, Tae-Suk's intentions are rooted in justice and career advancement as he aims to solve multiple connected murder cases. In a chilling twist, Dong-Soo instructs his right-hand man, Kwon Oh-Sung, to eliminate a rival using the killer's weapon, unknowingly further complicating the investigation. When Tae-Suk discovers this, a heated confrontation erupts between the two, especially when the ramifications of the serial killer’s actions lead to the case being escalated to the Major Case Squad.
As the investigation unfolds, each twist leads Tae-Suk deeper into the killer's web. He is soon faced with another kidnapping case indirectly tied to the killer's gruesome pattern, prompting him to have a mother deliver ransom money in hopes of tracking down the abductor. The chase takes an unexpected turn when they spot the killer, culminating in thrilling pursuits where both lawmen and criminals engage in intense battles for survival.
Ultimately, as the net tightens around the elusive Kang Kyung-Ho, played by Sung-kyu Kim, the lines between law and criminality begin to blur. Although Dong-Soo manages to confront and assault the killer, Tae-Suk’s intervention leads to the killer's arrest, even as he gains a wealth of evidence against him. The courtroom drama escalates with Dong-Soo’s unanticipated testimony revealing extensive ties to his past actions. The justice system decisively sentences Kyung-Ho to death, while Dong-Soo’s criminal dealings result in his arrest, aligning their fates in a gripping conclusion.
In a final twist, as Dong-Soo finds himself incarcerated alongside Taylor Kyung-Ho, the tension escalates dramatically, leading to a confrontation filled with impending uncertainty. With a sinister smile, Dong-Soo approaches the confined Kyung-Ho, the stakes of vengeance higher than ever.
