The story centres on a prosecutor who takes the law into his own hands. He will do anything to put an end to the greed of those who use their money and power to exploit others. He pays no heed to standard procedure and resorts to unlawful means to stamp out corruption in society. Jin Jung (Doh Kyung Soo) is a prosecutor with a deep sense of justice. He always stands up for the underdog and fights for them, guided by the principle of "an eye for an eye, a tooth for a tooth". He wants the victims to exact revenge ten times greater than the suffering they have endured. Shin Ah Ra (Lee Se Hee) is a senior prosecutor in the Criminal Investigation Department of the Central District Prosecutor’s Office. With her methodical approach to organising matters and her ability to assess situations objectively, Shin Ah Ra has become the office head’s right-hand woman. Furthermore, Shin Ah Ra has a sixth sense when it comes to politics and remarkable social skills, which enable her to maintain good relationships with her peers, both senior and junior colleagues at work, as well as with senior prosecution officials. Although she appears to be a completely different sort from the eccentric Jin Jung, Shin Ah Ra will look out for him and protect him more than anyone else.