In-ho (Gong Yoo) is an art teacher who takes up a position at a school for the deaf and hearing impaired in Mu-jin, following a recommendation from his former lecturer. On attempting to establish a rapport with his new students, he finds them deeply introverted and seemingly traumatised, but initially assumes that they are non-responsive simply because of their disabilities. However, as he slowly begins to get to know the children it becomes increasingly clear that something much more sinister is taking place in the school and before long he comes to the shocking realisation that the children are being physically and sexually abused by several of the other teachers.
When he decides to fight for the children』s rights and expose the crimes being committed at the school, In-ho teams up with human rights activist Seo Yu-jin (Jeong Yu-mi). But he and Yu-jin soon realize the school』s principal and teachers, and even the police, prosecutors and churches in the community are actually trying to cover up the truth.
Based on the novel "Dokani" written by Kong Ji-Young (published in 2009). The novel was inspired by a true incidents which occurred at a school for hearing-impaired persons in Gwangju, South Korea.