Hwang Shi Mok underwent brain surgery as a child to curb his violent temper, which left him devoid of emotions. Hwang becomes a prosecutor known for his piercing intelligence and logic, but he is ostracized because he lacks empathy and social skills. He is also one of only a handful of upright prosecutors who have refused to take bribes. One day, he encounters a stabbing victim while investigating corruption. He meets Lieutenant Han Yeo Jin at the crime scene. They join forces to root out corruption at the prosecutors’ office and solve a serial murder case.

In 1997, a mysterious ghost saved humankind and then disappeared. The mysterious ghost appears again 24 years later and helps a serial killer escape. Kim Sae Ha, Jung Sae Byeok and Song Eo Jin pursue the ghost for different reasons.