The family poodle has a litter of puppies, and Maddy's parents say that she can choose one for her very own. Maddy instantly falls in love with the runt of the litter, who was born with only three legs. Little Mia becomes Maddy's constant companion. When Finn and his family move in across the street, he joins Maddy and Mia on many of their adventures. Together, they learn the value of courage, acceptance, and friendship.