Amy wakes up from a cold, wet bathtub and finds herself under house arrest in an abandoned school. It's dark and scary, with weird graffiti on the mottled walls. During her house arrest, she can only rely on her thoughts. As a doctor, wife and grieving mother, she can never recognize the fact that her son has fallen asleep due to an accident, and believes that her son is also trapped in the school. In this hostile, supernatural purgatory-like school, Amy, who is trapped in darkness and despair, tries her best to find her son. She keeps breaking the rules of the "school". As Amy encounters the terrifying evil creatures living in the "school", terrifying supernatural powers and inner fears follow one after another. Is she fighting these terrifying creatures or her own inner demons?