Ui-gang is a retired hitman who has it all. One day his wife takes a trip to Jeju Island and leaves him with a favor. Her friend on the trip has a 17-year-old daughter, Yoon-ji, who will be left alone during their three-week vacation. Ui-gang reluctantly agrees to look after Yoon-ji to make sure she doesn't get into trouble. But she does. After some poor choices, and before she even realizes it, Yoon-ji finds herself in a situation far more dangerous than she ever imagined. But just as she is in over her head, her captors too will find themselves with more than they can handle when Ui-gang shows up to take her home.