On March 26, 1991, during local elections, five boys vanish while exploring a nearby mountain on a day off from school. Their parents push for an immediate police investigation, but the authorities are distracted by safeguarding the polling stations. Days turn into weeks, and thousands of officers scour the mountain for clues, yet nothing materializes. The nation follows the parents’ desperate pleas as their story captures hearts and minds, sparking a wave of theories—from North Korean spies to alien abductions—about what might have happened to the children.
In 1996, Kang Ji-seung, a career-driven documentary maker Park Yong-woo who has just been reassigned to the small town after a high-profile setback, returns with a single aim: to resurrect his name by solving the case. He teams up with a determined professor Jeon Kuk-hwan who is eager to prove himself by cracking a crime that the police could not solve. The professor’s theory starts to gain momentum when he uncovers a telephone recording of someone claiming to be one of the missing boys calling his own home. The mother Kim Yeo-jin does not seem shocked to hear her son’s voice, which unsettles the investigator and pushes the professors’ line of inquiry toward questions about what the boy’s family might be concealing. As they press, the entire household—parents and even the grandmother—appears to behave with strange, unsettled reluctance. The professor convinces authorities to dig up the boy’s home, but finds nothing conclusive. The accusation shatters the family’s reputation, and the father Sung Ji-ru dies without ever clearing his name. Soon after, Kang Ji-seung is reassigned back to the city, and the professor loses his university position, both casualties of a case that refuses to be put to rest.
Then, in September 2002, the remains of the children are discovered in the woods on the same mountainside the youngsters had described visiting. Two skulls show large holes and one bears strange indentations from an unidentified instrument, while their clothes are knotted in sailor-like knots and the scene yields bullet casings. The discovery rattles the country anew, and Seoul is shaken by news of two more children missing in the capital. Kang Ji-seung reconnects with the police officer who investigated the original disappearance a decade earlier, who reveals a chilling detail: on the night after the boys vanished, he encountered a mysterious young man who is always seen fishing nearby. The officer kept this quiet because Korea’s statute of limitations would bar any prosecution, even if the killer were caught years later. He chose to wait and watch for another crime to trap the suspect, hoping to finally bring closure.
Using a traced license plate, Kang Ji-seung locates the man and breaks into his apartment when he’s away. A disturbing cache awaits—a box of items belonging to children and stacks of books tied into sailor’s knots. He waits outside the building, intending to confront the suspect when he returns home. The next morning, Kang Ji-seung’s own daughter vanishes, only to reappear moments later, claiming a man driving a passing truck helped her. He races the truck to a slaughterhouse, where he confronts the suspect. The man refuses to confess but hints that he might be the killer. With no rock-solid evidence to arrest him, Kang Ji-seung watches as the suspect saunters away, leaving the mystery unresolved and the danger lingering over the city.
> The case lingers in memory, a careful balance of pursued truth and the limits of justice, as the investigators chase a thread that refuses to untangle neatly.
