Lee Ho-Chul (Jin Goo) works as a firefighter. He is your typical head of household, who loves his wife and daughter. Recently, the media covers an unsolved serial killer case. The case has nothing to do with Lee Ho-Chul, but he receives a text message that states “I will let you know who the serial killer is” and a photo. The photo is of a man holding a knife covered with blood and he is next to a murdered person.