He is a former solider who found his mother murdered when he returned from his service. Unable to get the justice she deserves, he He is a former solider who found his mother murdered when he returned from his service. Unable to get the justice she deserves, he is invited by an enigmatic man named Jang Sung-Chul, who lost his parents to a serial killer years ago, to become a part of a revenge call service to help victims like them and use his potential and knowledge to fight the corrupt society.