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.
Kyung-min lives alone in a one-room apartment. One day, she finds traces of a stranger breaking into her room and soon a mysterious murder case begins to unravel.
Ji-woo, an outcast at a prestigious private school, meets Hak-sung, the school janitor who is actually a mathematical genius who defected from North Korea.