The son of a spy decides to follow in his daddy's footsteps to secure his sister. After his dad botched espionage mission, North Korean Myung-hoon along with also his younger sister Hye-in are sent to a labor prison camp. In order to rescue his sister's life, Myung-hoon infiltrates that the South as being a defector that is teenaged and volunteers to become spy. He rescues her when she comes under attack, also meets another girl called Hye-in while attending high school in the South. South Korean Intelligence begin tracking him and discover the activities of Myung-hoon all the while their own government sends a assassin to eliminate him.