Xiao Erdong (played by Zhang Youhao), a teenager suffering from a rare disease but cherishing a "marathon dream", and Xiao Daming (played by Wang Yanhui), a taxi driver father who stubbornly forced his son to prepare for the "blind life". The father and son who did not understand each other "exchanged identities" in a marathon race and stood side by side at the starting line... The film tells a story of living with love through a father and son from a single-parent family who have different attitudes towards "destiny".