On March 26, 1991, the local elections are being held. Since it is a school day off, the five boys set off to the nearby mountain and never return. Their parents try to get the police to investigate right away, but the authorities are more concerned about guarding the election poles. Days later, thousands of police set on the mountain to search for clues as to what may have happened but nothing turns up.

In 1996, a career-driven documentary maker, Kang Ji Seung is transferred to the small town after being disgraced for rigging an award-winning documentary. He then decides to investigate the case in the hopes of making a comeback. He teams up with an equally ambitious professor who hopes to make a name for himself by solving the crime where police failed. The professor’s theory, which seems to have quite a bit of compelling evidence behind it, takes the pair in a direction that the police were reluctant to investigate.

Based on "Frog Boys", a true unsolved murder case from the early 1990s.