Lin Bei Xing is a young woman, who is about to enter her 30s, suddenly finds that her life has gone awry when her fiancé, Zhan Yu, whom she has been in love with since high school, cancels their engagement to date her best friend.
Hoping to rekindle memories of their love, Lin Bei Xing invites Zhan Yu to return to their high-school premise in their old school uniforms for a day. While waiting for Zhan Yu in the rain, she activates her old phone and unknowingly travels back in time.
Lin Bei Xing returns to the age of eighteen. The third year of high school is a nightmare, but Lin Bei Xing decides to retake the college entrance examination and forget Zhan Yu. However, an accidental encounter with Zhang Wan Sen after the college entrance examination becomes the trigger of Lin Bei Xing’s time and space journey.