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