Kim Hye In is a high school student from a poor background. She becomes the only witness to the murder of a high school girl. In exchange for her silence on the murder she witnessed, she is offered a chance to study at Cheongdam International High School, the most prestigious high school. There, Kim Hye In meets Baek Je Na, the leading suspect of the murder and the most powerful student at Cheongdam High. They engage in psychological warfare full of tension and a fierce power struggle.