Park Moo Jin and Kang In Ha is 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 two children to the fullest, but their peaceful days suddenly turn into one of a hellish experience. Their son, Park Sun Ho, who is in his 3rd year of middle school, becomes a victim of school violence and gets seriously injured. Park Moo Jin and Kang In Ha try to reveal the truth behind the assault that hurt their son. Their daughter, Park Soo Ho, who attends a year lower at the same school, also decides to seek the truth behind her brother's attack in her own way. Meanwhile, Oh Jin Pyo and Seo Eun Joo is a married couple who are both from wealthy families. Oh Jin Pyo is the chairman of a private school foundation inherited from his family. The couple has never experienced failure or lacked anything. However, that fact quickly changes when their son, Oh Joon Seok stirs up trouble at school. This sudden change forces Oh Jin Pyo and Seo Eun Joo to frantically try to cover up their son's misbehavior in order to safely secure their place in the society. The two families get entangled into a complicated case as they both desperately strive for clashing goals to find a 'beautiful world' in their lives.