Park Moo-Jin and Kang In-Ha are a married couple. Park Moo-Jin works as a high school teacher and Kang In-Ha runs a bakery. They enjoy their lives with their children. Their peaceful days soon turn into a hellish experience. Their son, who is in the 3rd grade of middle school, is seriously injured due to school violence. Park Moo-Jin and Kang In-Ha try to reveal the truth.