Detective Young Gun (Hong Young Geun) specializes in frivolous cases, due to his money woes. One day, a beautiful woman named Song Hyun (Choi Song Hyeon) comes to his office and asks Young Gun to kill a man, but he refuses citing his profession's moral honor code. Nevertheless, Young Gun is strongly attracted to the beautiful woman and follows her when she leaves his office. Young Gun then witnesses Song Hyun getting killed in a car accident. He is traumatized over her death and decides to investigate her background. Surprisingly, a woman, who looks exactly like Song Hyun, appears in front of Young Gun. Young Gun knows that the woman is Song Hyun from 3 days in the future. Song Hyun then asks Young Gun to save her life and he accepts her request. Young Gun has only 3 days to save her, but first he has to get a time machine.