Ui-kang (JANG Hyuk) is a retired hit man who doesn’t want any trouble. One day, his wife decides to go on vacation with her girlfriend, but before she leaves, asks for one favor from him - to take care of her friend's 17-year old daughter, Yoon-ji (LEE Seo-young, GWSN Kpop girl group), while they are away. Thinking it should be an easy enough job, he agrees. But Yoon-ji is determined to take advantage of the opportunity and soon gets involved with some bad characters. However, Ui-kang is on the case and saves her life. That is until things get much more complicated -- and SERIOUS! Yoon-ji is being targeted and kidnapped by a teenage trafficking unit and Ui-kang is suspected of murder. Determined to keep his promise to his wife, Ui-gang must figure out, and fight through, the many layers involved to get the girl back, safe and sound.