Da-Eun (Son Ye-Jin) has completed graduate school and is set to become a newspaper reporter. She lives with her father Son-Man (Kim Kap-Soo) who lovingly refers to her as "my heart". Although her father does menial work, Da-Eun is proud of him.
One day, Da-Eun goes to the movie with her boyfriend Jae-Kyoung (Lee Gyu-Han) and friend Bo-Ra (Jo An). They watch a movie that is based on a real life unsolved crime. A man kidnaps a boy and demanded ransom from the parents. The child is later found dead and the killer is never heard from again. The only clue the police have to the killer's identity is the ransom phone call he made to the parents. At the end of the film, they play the actual recorded audio from that phone call. When Da-Eun hears the voice she becomes frozen. The man's voice sounds eerily like her father and he also uses the phrase "It Ain't Over 'til It's Over" which her father always favored.
When Da-Eun gets back home, she looks up the crime that took place nearly 15 years ago on the internet. She finds a recording of the killer's voice and listens to it again. Da-Eun becomes awash with horror and also guilt for even suspecting her father as the killer. There's also only a few days remaining before the unsolved crime runs into its statute of limitations. What will Da-Eun do? Meanwhile, a man (Lim Hyung-Joon) from her father's past suddenly appears.
