Chul Woong, a high school teacher, had lost his fiancee to a tragic murder case just before their wedding. 10 years have passed, but he is still haunted by painful memories. Sang Won, the police detective formerly in charge of the case, is still dedicated to solving crimes than climbing the ladder, and is a devoted father to his only daughter Jung Hyun. One day, Chul Woong enters Sang Won and Jung Hyun’s life when he becomes her teacher, and for an unknown reason, Jung Hyun innately has feelings towards him and the secret that needed to be kept hidden reveals itself.