The Gangster, the Cop, the Devil

A stranger crashes into a man's car and, while taking photos of the damage for an insurance claim, murders him. The killer then vanishes from the scene, establishing a pattern that will link later attacks. The opening sets up a dangerous serial killer on the loose.

Detective Jung Tae-suk arrives to inspect the aftermath and quickly theorizes that the incident resembles the work of a serial killer. His assessment clashes with his commanding officer's reluctance to label it as a serial case. The tension foreshadows a high-stakes pursuit ahead.

On his way home from a meeting, Jang Dong-soo is struck by the same killer who pursues him. A brutal fight ensues, leaving both men battered and the killer escaping after the attempt on Dong-soo's life. The incident triggers a grudging interest in vengeance from Dong-soo.

Dong-soo recovers from his injuries in the hospital while his right-hand men suspect a rival gang is responsible. He concludes the killer's moves are random and purposeless, fueling his resolve to hunt him down. The hospital becomes the stage for a fragile alliance forming later.

Tae-suk visits Dong-soo in the hospital and urges cooperation to catch the killer and solve the murders. Dong-soo refuses the police help, preferring to hunt the killer himself. He demands his own men to locate the killer first.

Growing pressure forces both men to team up, with Dong-soo offering manpower and financial support in exchange for the chance to kill the killer first. Tae-suk agrees that catching the killer could solve multiple cases and boost his career. The arrangement is pragmatic, not ideal.

Dong-soo orders his trusted man to use the killer's knife, stained with earlier victims' blood, to kill rival Heo Sang-do. The act demonstrates the killer's reach and deepens the conflicts between the two factions. Tae-suk learns of the illegal killing and the case is moved to a major crimes unit.

At Sang-do's funeral, the killer appears and informs Sang-do's second-in-command that Sang-do was killed by the killer's knife, but by someone else. The confession fragment unsettles both police and gang members. It foreshadows that the killer could be closer than anyone suspects.

Tae-suk and Dong-soo search the killer's car for evidence and are ambushed by Sang-do's henchmen. In the clash, Sang-do's right-hand man is killed but Tae-suk and Dong-soo manage to survive. The incident intensifies the case and escalates the violence.

Dong-soo buries the dead and Tae-suk is reassigned to a kidnapping case. While solving it, he spots the killer and a chase ensues, though the killer escapes again. The chase confirms the killer's continued freedom and the danger he poses.

Forensic tests reveal that the killer is a missing person, aligning his elusive behavior with disappearances. Tae-suk informs Dong-soo and plays a voice clip to confirm that the missing person is indeed the killer. The discovery narrows the suspect pool and heightens tension.

Dong-soo helps a high school girl by giving her his umbrella, only to learn she is later murdered and his umbrella is found at the crime scene. The clue links a random act of kindness to the killer's escalating violence. Dong-soo and Tae-suk intensify their search in the area.

The pursuit narrows to a car chase where the killer kills Oh-sung, but Dong-soo finally incapacitates him. Dong-soo intends to torture and kill the killer, but Tae-suk arrives and crashes his car into the hideout just as Dong-soo is about to strike. The killer is brought down and arrested.

With little conclusive evidence, Tae-suk urges Dong-soo to testify. Dong-soo provides decisive testimony and even predicts a stab wound on Kyung-ho, using the killer's actions to frame him for Sang-do's murder. Kyung-ho is sentenced to death, but Dong-soo is also arrested for his illegal activities.

Tae-suk is promoted to a higher position, while Dong-soo is sent to the same prison as Kyung-ho due to his earlier misdeeds. In a final twist, Dong-soo confronts Kyung-ho in his cell with a rope and a menacing smile, signaling his grim satisfaction. The ending leaves the consequences of their alliance stark.