Sung plays a woman who has never taken a risk in her life. She has been dating the same man for seven years and is planning to get married next month. Then one day she meets a handsome stranger, played by Cho Dong Hyuk, who persuades her to spend one day with him. Maybe it was a mistake to accept his proposal, but over the next twenty-four hours she will experience a level of excitement and intimacy, as well as confusion, that she has never experienced before, and could change her life forever.