After the death of her younger brother Han Byeol and the disastrous effect it had on her family, Han Yeol Mu can no longer trust government authorities. Realizing that Ku Dong Chi, someone she's interested in, is involved with the only evidence left from her brother's death, Yeol Moo becomes a prosecutor. Yeol Mu strategically starts working for Dong Chi to avenge her brother's death. Ku Dong Chi had plans to go to medical school, but the day he got his scores for the college entrance exam, he failed to save Han Byeol from getting kidnapped. The extreme guilt he felt led him to become a prosecutor. Dong Chi starts to develop feelings for Yeol Mu, who randomly returns as a new junior prosecutor in his office. But she is only interested in revenge and shows hostility. Knowing that Yeol Mu thinks of him responsible for her brother's death, Dong Chi tries to set things straight by sharing with Yeol Mu all the data he's been collecting since the kidnapping.