In 2008, Xia Ye receives a mysterious package from the Post Office of the Future, which contains audio cassettes from the late 1990s and an old cassette player. She listens to them on the train to Qingdao and hears the voice of the 17-year-old Ke Da. Back in the hot summer of 1997, Ke Da had fallen for Xia Ye during their senior year at high school, and the two had expressed their feelings to each other via audio cassettes. Li Fusheng, a guy who Ke Da met at swimming classes, runs the Post Office for the future, accepting messages for the living or the dead to be delivered sometime in the future. He believed that the dead live on at the Centre of the World, where they meet because of love.
