A paragliding mishap drops a South Korean heiress in North Korea -- and into the life of an army officer, who decides he will help her hide.

Kyung-chul is a dangerous psychopath who kills for pleasure. Soo-hyeon, a top-secret agent, decides to track down the murderer himself. He promises himself that he will do everything in his power to take vengeance against the killer, even if it means that he must become a monster himself.

Based on actual events that took place at Gwangju Inhwa School for the hearing-impaired, where young deaf students were the victims of repeated sexual assaults by faculty members over a period of five years in the early 2000s.