Kyung-Yoon Kim Kang-woo and Eun-Ju Kim Gyu-ri investigate a grisly murder that rocks a city’s elite. The victim, a wealthy entrepreneur, is found slashed more than twenty times, with blood staining the apartment and little sign of a struggle. The killer is meticulous, leaving almost nothing behind except a single hair strand, and the early clues point to a male culprit with AB blood. Amid the case, Kyung-Yoon’s personal life spirals as his girlfriend asks for a breakup, claiming he loves someone else and even blurts out that person’s name while drunk. The tension between a demanding job and a fragile romance threads through the investigation, adding a personal weight to every move.
Shortly after, a second murder mirrors the first with the same brutal MO, suggesting a connected pattern despite the victims appearing unrelated at first glance. Delving into their histories, the team uncovers a shared thread: both victims were stationed at the same military base years earlier. A month before discharge, they were transferred to another base along with a third man named Jong Ha, which leads the detectives to wonder if Jong Ha could be the next victim or perhaps the killer himself. The case tightens its grip as new linkages emerge, and the search widens beyond the immediate crime scenes to the long-ago network that still echoes in today’s killings.
As the narrative unfolds, a string of flashbacks introduces Yoon-Suh, Kyung-Yoon’s old friend who was gentle and seemingly fragile. Kyung-Yoon protected him from bullies in youth, but a moment of anger turned that protection into a painful rift when he told Yoon-Suh to man up. Motivated by old loyalties, Kyung-Yoon independently traces Yoon-Suh’s steps, contacting a former military acquaintance who explains that Yoon-Suh had joined the service only because someone urged him to “man up.” What follows is a brutal revelation: Yoon-Suh endured abuse and rape at the hands of the trio, a truth that begins to reshape the investigators’ understanding of the murders and the motives behind them.
The investigation drives Kyung-Yoon to a confrontation with Jong Ha, whose dismissive arrogance amplifies Kyung-Yoon’s anger. Jong Ha’s cruel joke about Yoon-Suh’s experiences fans the flames, and a scuffle leaves Kyung-Yoon bruised while Eun-Ju reaches out with news that Jung Ho has been found dead. The mounting tension pushes Kyung-Yoon to a troubling conviction—that Yoon-Suh might have undergone a sex change and become the killer. He shares his suspicions with Yoon-Suh’s sister, Lee Hye-Seo Kim Sung-ryung, who tearfully counters that such a theory isn’t true. At the same time, Eun-Ju uncovers a secret passage from the first crime scene leading to the kitchen, where a cook with a weapon identical to the murder tool attempts to flee but is quickly captured.
In a crucial turn, Lee-Hye-Seo reveals that Yoon-Suh’s fate is more tangled than anyone expected. The sister explains that Yoon-Suh met the victim by coincidence and hoped for an apology, but the real killer’s identity soon shifts the entire moral equation. The forthcoming disclosure identifies the killer not as Yoon-Suh, but as Kyung-Yoon’s girlfriend—the person he had planned to marry—introducing a shocking romantic motive behind the serial violence. Kyung-Yoon confronts his own past as the truth about the killer’s identity emerges, and the pursuit becomes a breakup of trust and a dangerous flight from the law as Kyung-Yoon and his partner seek to escape on a bike while police close in. The discovery reframes the story: Kyung-Yoon had carried hidden feelings for Yoon-Suh, a secret he had buried under a veneer of control and propriety, a truth that now collides with the brutal consequences of their shared history.
The story complicates further with Eun-Ju’s subtle, painful knowledge. She had realized that Kyung-Yoon killed Jung-Ho by taking Jung-Ho’s lighter from the crime scene, yet she keeps silent out of love for Kyung-Yoon. The final tangles deepen as it’s revealed that Yoon-Suh did not kill anyone; instead, the cook kills the two rapists who had sexual relations with the singer involved in the case, revealing his own confession of love for her as he kills her at the end. With these revelations, the film closes on a note of layered tragedy and ambiguous loyalties, where love, guilt, and memory contort the truth in ways that linger long after the credits roll.
