Xiao Erdong is a young man who suffers from multiple sclerosis - a disabling disease of the brain and central nervous system - and eventually goes blind. But he has long harboured the dream of running a marathon, just as his late mum did before she died from the same disease. Erdong is raised by his father Xiao Daming who is a taxi driver and stubbornly forces his son to live a certain way. Nevertheless, he helps his son to achieve his dream of running in a marathon.