Due to past experiences of intense fear, some people suffer from psychological distress known as trauma. People with severe traumas, which are unbearable, develop supernatural abilities. However, using these abilities dredges up memories from the past, and the pain becomes overwhelming. Those who cannot bear the pain eventually transform into monsters.
A rumor spreads in a school in Seoul about a monster with a head made of flowers living under the bridge behind the school. The school bullies try to force Park Dohyun, a quiet student, into the bridge, but his sister intervenes and stops them.
However, on that night, due to pressure from the bullies, Dohyun accidentally witnesses his sister entering the bridge in his place. He hurriedly follows her when he realizes shes inside, but she meets her end at the hands of the monster within
