The Execution

Detective Seo Do-cheol's Violent Crimes Investigation Unit raids an illegal gambling den, initiating their investigation. This operation sets the stage for uncovering the pattern of crimes and the involvement of a mysterious killer. The scene marks the beginning of the police's active pursuit of justice against illicit activities.

A viral video surfaces showing a masked killer executing an art professor who had raped a student, leading to her suicide. The police quickly realize this murder is part of a disturbing pattern, where victims were past perpetrators of crimes. This revelation raises concerns about a serial killer targeting wrongdoers seeking justice.

Authorities confirm that each victim was involved in a crime and was executed in the same manner as their victims. This pattern indicates the killer, dubbed 'Haechi' by the media, is systematically targeting those who escaped justice. The investigation intensifies as more similar murders occur, hinting at vigilante justice.

YouTuber Editor Justice begins covering the murders, framing Haechi as a vigilante exposing flaws within the legal system. His videos go viral, garnering public support for the killer's cause. The media's portrayal influences public opinion and increases pressure on the police to find Haechi.

A warning surfaces that ex-convict Jeon Seok-woo, responsible for a drunk driving incident that resulted in a pregnant woman's death, is the next target. Despite mounting public outrage, Seo's team is instructed to protect Jeon, leading to his swift transfer to a safe house. This sets a tense atmosphere for the team.

While under police protection, Jeon Seok-woo escapes from the safe house but is later found dead under suspicious circumstances. This raises questions about the killer’s infiltrating nature and the safety of witnesses, complicating the investigation. The team begins to suspect internal threats or skilled adversaries involved.

A staged confrontation on a live stream at Namsan goes awry when Sun-woo brutally assaults a man believed to be Haechi. It is later revealed the victim was an actor hired for content, exposing Sun-woo's aggressive approach. The incident strains team trust and fuels suspicions about Sun-woo’s true motives.

Signs emerge linking Sun-woo to the killer, including his martial arts skills and knowledge of police tactics. Forensic evidence reveals he used leg-based choking techniques similar to those found on Jeon's killer, raising suspicion that he may be Haechi. Detective Seo begins to question Sun-woo’s integrity.

A former soldier, Min Kang-hoon, is arrested after a violent confrontation with a biker gang that he kills with his car. During a rooftop fight, Sun-woo nearly kills Kang-hoon with an extreme jiu-jitsu move, but police intervene. The arrest suggests Kang-hoon might be connected to the killer’s pattern.

Forensic analysis and investigations reveal that Jeon was killed using leg-based choking techniques, consistent with Sun-woo’s methods. Seo deduces that Sun-woo has been impersonating or collaborating with Haechi all along, implicating him as the real killer. Tensions peak as Seo considers confronting Sun-woo.

Sun-woo kidnaps Editor Justice and lays a trap for Seo, forcing a choice between saving his son and another innocent woman. Seo's team rescues his son just in time, leading to a brutal final showdown. Seo fights Sun-woo fiercely, forcing him into a desperate situation, hinting at a climactic resolution.

Seo nearly kills Sun-woo in their confrontation, but Seo manages to revive himself and insists Sun-woo face justice. As emergency services arrive, Seo’s emotional resolve is clear. A post-credits scene reveals Sun-woo has escaped custody, leaving open the possibility of future conflict.