Summary
Highlights
Flashback to 15 years ago: Ha-kyung's failed ransom exchange with counterfeit money. In the present, Ha-kyung, still haunted, arrives at the train station. Bom's mom places a tracked duffel bag. Amidst military personnel, the kidnapper takes the bag, removes the tracker, and escapes. Cheong and Kang give chase.
The movie begins with Ha-kyung's nightmare of a past tragedy. Detective Cheong visits her 15 years after her daughter Seo-jin's kidnapping, with the statute of limitations nearing. Ha-kyung is furious he hasn't found the culprit and shows him her own extensive investigation.
Cheong revisits the crime scene and finds a mysterious flower. Surveillance footage reveals an unidentified man. Following tire tracks, they find a Carnival vehicle without a license plate, but a distinctive sticker. Cheong spots the vehicle and a suspicious man, leading to a chase through a market and restaurant, but the suspect escapes after an encounter with Ha-kyung.
The stolen license plate leaves a dead end. Ha-kyung suggests the man visited other places, but Cheong, defeated as the statute of limitations expires, tells her to give up. The next day, Cheong, burdened by guilt, resigns and burns Seo-jin's case files.
An old man named Han reports his granddaughter, Bom, missing. The kidnapper uses a voice changer and demands a ransom. Ha-kyung starts her own investigation, finding a bank logo on an umbrella left by the culprit. Bom’s mother receives a call and finds a Polaroid picture of her daughter, mirroring Ha-kyung's past experience.
Officer Kang notices the current kidnapping's striking similarity to Seo-jin's case. Cheong, alerted, believes it's the same kidnapper. The kidnapper instructs Bom's mother to drop the money at the same train station used 15 years ago.
Han is revealed to have been tricked into wearing a military uniform for the ransom. The police grow suspicious of Han due to inconsistencies and evidence matching his DNA. Cheong, however, believes Han is not the true culprit, noting the kidnapper's cleverness and suggesting someone else framed him.
Ha-kyung's investigation leads her to a house in the countryside, where she finds clues confirming her suspicions. Cheong finds a damaged tape from the warehouse where Han was held, revealing the kidnapper coaching Bom. Cheong discovers a shocking twist: the voice from the current kidnapping tape matches the old one, and it was engineered by Ha-kyung using her old recording.
A flashback reveals Ha-kyung, seeing Han happily with his family, kidnapped Bom for revenge. Cheong tracks Ha-kyung and confronts her, agreeing to let her keep Bom until the trial. Cheong then confronts Han, revealing his knowledge of Han being the original kidnapper. A flashback shows Seo-jin's tragic death during her escape from Han. Cheong confronts Han with the truth, and he confesses, allowing Bom to be reunited with her family. Han is sentenced to 15 years, and Ha-kyung visits her daughter's memorial.