Wendy's life would be perfect if it weren't for her younger sister, Katie. Katie spies on her and tattles on her. Worst of all, Katie is terrific at everything she tries!

Wendy would like to prove herself and to "Katie the Pest" that she can be successful too. So, Wendy signs up for riding lessons. Wendy is sure that Katie, who's less athletic, won't be interested. But within a week, Katie has enrolled in the same class!