Arthur gets fired by his new piano teacher, Dr. Fugue, for neglecting to practice, and then must find a way to convince Dr. Fugue to give him a second chance.
Unable to think of an idea for a science fair project, Arthur borrows a model his father made in third grade but feels bad about it even before he gets into trouble.
Arthur's Grandma Thora, a marbles champion, trains him for the first-ever Elwood City Marbles Tournament, but does not tell him that she will compete against him.
Mom and Dad are ready to go out for the evening, but Arthur and D.W. are worried that their surprise babysitter might be a pirate, robot, or even Mr. Ratburn.
Arthur tries valiantly to save his sister from being disappointed when Mary Moo Cow, slated to entertain at D.W.'s birthday party, cancels at the last minute.
Arthur and his friends get very involved in training for a race to raise money for a literacy drive, but Fern, who just wants to rest and read, seems to have the best strategy.