Sook-hee is a trained assassin who was born to kill. She was just a little girl when the training started in Yanbian, China. After the death of her mentor, when the chance of starting a new life was given to her, she came to South Korea as a government agent. They promised her that she will be free after ten years of service. So she begins her new life as a theatre actress. But soon two men Joong-sang and Hyun-soo appear in her new life. And she started to find deep dark secrets about her past. Eventually she take matters into her own hands.
In 1995, five serial murder cases took place. Wataru Makimura took charge of the murder cases and tried to catch the serial killer. Due to the killer's trap, Wataru Makimura's superior was killed. The serial murder case has been unsolved to this date. 22 years later, a murder memoir "Watashi ga Satsujinhan desu" is published. The author describes himself as the killer responsible for the five unsolved serial murder cases. The author, Masato Sonezaki, has an attractive appearance and appears at a press conference for his newly published book.