What happens to the criminals who escape the law? Ha Dae Cheol (Joo Sang-wook) is a righteous prosecutor who works tirelessly to go after criminals and enforce justice. But despite his best efforts, some hardened criminals are able to escape punishment and go free. That's when the prosecutor-by-day dons his disguise and goes after the criminals as a masked-vigilante-by-night! Yoo Min Hee (Kim Sun-ah) is a police detective in charge of the violent crimes division. As she follows the trail of the masked vigilante, will she help or hinder his cause?