Sometimes you have to take the law into your own hands: During the day, Ha Dae Chul is a judicious and law-abiding prosecutor, but by night, he dons a mask and grievously punishes criminals who have fallen through the system. Detective Yoo Min Hee, lead detective of the violent crime division, is hot on the trail of the masked vigilante's reign of righteous pain, but has no idea that the man under the mask is really on her side.