When heinous criminals avoid punishment from the law, all citizens over 18 years old receive a text message polling them on whether that person should receive the death penalty. If more than 50% respond in favor of the capital punishment, that person is killed by "Dog Mask" - unknown, working in virtual world persona. Meanwhile, the police chase after "Dog Mask" and three people become involved because of it: Kim Moo Chan leader of the First Investigation Team at the Southern Police Agency, Kwon Seok Joo former famous legal scholar, who killed the rapist who attacked his young daughter and then turned himself in to the police and Joo Hyun - a police officer who has worked at the Cyber Safety Bureau at the Seoul Metropolitan Police Agency for 5 years.