Season 1: A high school student dreams of becoming an architect. However, she had to drop out of school after suffering from brutal school violence. Years later, the perpetrator gets married and has a kid. Once the kid is in elementary school, the former victim becomes her homeroom teacher and starts her thorough revenge towards the perpetrators and bystanders of her bullying days. Season 2: Moon Dong Eun's silent fury against those students that horrifically abused her during her high school years continues to burn inside of her. She meticulously executes her plan to inflict ultimate pain on her tormentors. Meanwhile, the sudden disappearance of Son Myeong Oh has gotten the attention of the police and his friends. Joo Yeo Jeong follows Moon Dong Eun and is willing to do anything she asks in her pursuit of revenge. Before Moon Dong Eun begins her final moves, she offers her nemesis Park Yeon Jin a chance to save herself if she turns in to the police, but Park Yeon Jin has her own plans to stop Moon Dong Eun. A violent and bloody game of nerves plays out between these rivals.