A story about a father and son who have different attitudes towards life. Because of a marathon, different routes lead them to the same goal as they push themselves beyond their limits. It tells the story of a single-parent household. Xiao Erdong is a young man with a congenital disease and a "marathon dream" while his father Xiao Daming is a taxi driver who stubbornly forces his son to live a certain way. The two people who never understand each other "exchange identities" during a marathon and stand side by side on the starting line...