The Chase

Shim Deok-su starts his day by visiting Mr Choi to demand rent, showing little compassion for his ailing tenant. Charity workers from a local church arrive to plead on Choi's behalf, but Deok-su remains unmoved. The scene establishes his gruff, predatory attitude and sets the tense mood for the neighborhood.

While Deok-su goes about his routine, police clear the street and uncover two dead bodies: a local drunk and an elderly pensioner. The double tragedy heightens fear in the neighborhood and foreshadows the killer's pattern. Deok-su's life intersects with crime as rumors begin about suspicious deaths.

That evening, Choi cooks an extravagant dinner and reveals he once worked as a police detective. He argues that the earlier deaths were murders committed by someone testing the method on the elderly before targeting others. Deok-su remains skeptical but intrigued by the detective's instincts.

That same night, an unseen assailant murders Mr Choi and arranges his body as a suicide to mislead investigators. The brutal crime confirms the detective's suspicions and raises the stakes for the tenants. Deok-su is drawn deeper into the mystery as a potential witness and target.

A few units down the corridor, another tenant, Ji-Eun's roommate, is found murdered with a slit throat. The string of killings intensifies fear in the building and attracts attention from investigators and residents alike. Deok-su begins to see a pattern emerging across the flats.

Ji-Eun returns home to find her roommate dead and is suddenly attacked as the killer strikes again. The attacker bashes her head and kidnaps her, leaving the apartment in chaos. The danger now centers on Ji-Eun, whose fate becomes urgent for the investigators.

Rumors and fear shift toward Deok-su as the community singles him out as responsible for neglecting tenants. The neighborhood's anger grows as suspicion spreads, while Pyung-Dal remains unconvinced and pursues the truth. The case tightens its grip on the building.

Retired Detective Pyung-Dal arrives and refuses to accept Deok-su's guilt. He uncovers evidence that Mr Choi was not suicidal and connects a string of pensioner- and young-woman murders from thirty years earlier. His discoveries begin to weave the current cases into a long-running pattern.

As Pyung-Dal digs deeper, it becomes clear that Ji-Eun matches the historical victim profile. Deok-su and the detective realize the kidnapper will strike at her, so they resolve to act instead of waiting for the police. The two form a fragile alliance to protect Ji-Eun.

Deok-su hurries back to Ji-Eun's apartment after the new information, hoping to find her safe or still alive. They mount a tense search through the building where the murders occurred. Time is running out as the killer could strike again at any moment.

A run-in with a gang connected to the murdered woman leads them to Ji-Eun's apartment, where they discover the severed head of Ji-Eun's roommate in the refrigerator. The grisly find confirms the killer's brutal methods and deepens the danger to Ji-Eun. Deok-su and Pyung-Dal realize they must act quickly.

In a final twist, the mild-mannered doctor, praised for his volunteer work and devotion to his paralysed wife, is revealed as the killer. The seemingly kind physician orchestrates the murders while maintaining his public image. Deok-su and Pyung-Dal confront the truth and race to save Ji-Eun.