Fei will get the best birthday present ever if he finishes his homework. That is what his mother has promised him. But it's the last day of summer, and Fei hasn't received anything yet. On this day, the two of them have been arguing all day. After their big fight, Fei, frustrated, is sorting through his schoolbag and suddenly finds a cassette tape he has forgotten. It's part of a school assignment, recording a summer day he had forgotten entirely about. With time running out, Fei and his mother decide to renew their relationship, embark on a daring plan to rewind the clock, and experience the last day of summer together.