Nancy and her friends are off on an apple-picking adventure! They are headed to the Kids Apple Festival, where they will pick apples, go on a hayride, and work their way through a cornstalk maze. Bess is excited about the applesauce-eating contest -- after all, apples are her favorite food! And the winner gets a whole basket of River Heights Reds -- a brand new type of apple!

But when the basket -- and all the apples in it -- vanishes, Nancy knows she has to get to the core of this mystery. Can she figure out who the bad apple is, or is this festival on the verge of an apple emergency?