Christopher McDougall's new running partner, Sherman, is ill-tempered, obstinate, and often so uncooperative that Christopher leads him with a rope. Sherman is also a donkey. What's more, Sherman has good reason for his bad temper; he was neglected and abused by his previous owner, and would have died had it not been for the intervention of one of McDougall's neighbours. With Sherman now safe, it falls to Christopher McDougall to lead him up the long path back to health, which he does with the aid of a menagerie of animals on his farm in rural Pennsylvania. But while Sherman's blossoming friendship with the farm's goats and a kitten named Polly may be doing wonders for the donkey's mental health, McDougall quickly realises that his new charge needs physical activity and a purpose in life. This leads them to the world of Burro Racing. Burro Racing - running a marathon accompanied by a Donkey - turns out to be perfect for Sherman and for McDougall who soon sets his sights on participating in the World Championship Pack Burro Race in Fairplay, Colorado, where Burro Racing was invented. As McDougall learns how to care for his new companion and meets the men and women who have fallen in love with Burro Racing, he discovers how working with animals can teach profound lessons about what it means to be human.