When the most popular female student, Jeong Soo-ah gets stabbed in her home, her classmate Kim Han-su got framed for her murder. Gi Moo-hyeok, a shrewd lawyer from prestigious Songha law firm, is assigned to defend Kim Han-soo. To avoid a scandal the school administrators went out of their way to keep the murder under wraps. Gi Moo-hyeok tries to persuade Kim Han-soo to take a plea deal and admit to the murder in exchange for a lighter sentence. But Han-soo refuses.

Without Kim Han Soo’s cooperation, Moo-hyeok tries to create reasonable doubt during the trial by suggesting that Jeong Soo-ah is an escort and any of her male clients could have attacked her. This enraged Han-soo who had no choice but to put the blame on himself to protect Soo-ah’s reputation. 

The case crashed which also saw the end of a Moo-hyeok’s career. To regain his reputation as a lawyer, he goes undercover as a substitute teacher named Gi Kang-jae. There he discovered the online and physical bullying the students in the school are perpetrating. Together with the PE teacher, they team up to uncover a secret society of privileged students who control fellow students and even teachers.