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. After rescuing Sherman from a neglectful owner and almost certain death, Christopher McDougall plunges into the world of Burro Racing -- running a marathon accompanied by a Donkey. His aim is to rehabilitate Sherman, to give him purpose, and to participate in the World Championship Pack Burro Race in Fairplay, Colorado, where Burro Racing was invented. But along the way, 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.