Molly wants a horse of her own, but when her father's mare gives birth to a mule, Molly changes her mind and raises the newborn.

Suzy Mule follows her friend Bruce the Goose on his way south, and when they arrive at Stu's Dude Ranch in the desert they decide to stay.

Until they see their two stubborn mules finally resolve a behavior problem, Benny and Sally refuse to believe that sharing could bring happiness.

In 1852, recently orphaned, thirteen-year-old Mateo becomes an "arreiro," or mule driver, bringing supplies to California gold miners and searching for the notorious bandit who stole his horse, but when he learns that Yankee squatters are threatening to take the ranch he grew up on, Mateo heads for home.

Junia, a dedicated mule with an important job, assists in delivering books and reading material to people in the Kentucky hills and woods during the Great Depression.