A North Korean spy's son decides to follow in his dad's footsteps to guard his sister. After his daddy's botched espionage assignment, also his young sister Hye-in and North Korean Myung-hoon have been provided for a labor prison camp. In order to rescue his sister's own life, Myung-hoon volunteers to be spy and infiltrates the South as a teenaged defector. While attending high school in the South, he meets another girl named Hye-in, and rescues her as she's under attack. The activities of Myung-hoon are so on discovered by south Korean Intelligence and start tracking him all of the while their government sends a vicious assassin to expel him.