High school student Ye Xianglun (Jay Chou) comes from a single-parent family and attends the school where his father (Anthony Wong) teaches. Influenced by his father, he loves music and is an excellent piano player. One day, a new classmate named Lu Xiaoyu (Gui Lunmei) who also loves playing the piano comes to the class. The two get along well and are inseparable, and their feelings are gradually warming up. However, Xiaoyu is always quite mysterious and often plays a beautiful but unpublished song. Whenever Xiaolun wants to know more about Xiaoyu, she often hesitates to speak and just says it is a secret. But one day, after a misunderstanding, Xiaoyu never comes to class again. Xiaolun, who misses Xiaoyu and is confused, is determined to find out this secret that cannot be told.