Arthur and his friends try to find a substitute to attend the Father's Day picnic with Buster, whose father is not around much since his parents' divorce.
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 and his friends face a number of dilemmas trying to get ready for school in the morning, and Arthur is both hindered and helped by his little sister.
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.