Ha Na (Im Joo Eun) and Doo Na (Park Ji Yeon) were twin sisters who were very close to each other until Doo Na died a terrible death. One day, the usually bright and energetic Ha Na finds herself changing. She has superhuman strength and can do things that nobody can. Ha Na realizes that Doo Na's spirit has inhabited her body. Shin Ryu (Lee Seo Jin), a criminal psychoanalyst, uses Ha Na's powers to kill people that cannot be punished by the law.