Arthur is looking forward to his family's trip to the circus, but he gets chicken pox, and is unsure if he will get better in time for the circus. When Grandma Thora visits to take care of Arthur, D.W. gets jealous of the attention he gets and tries to pretend she has chicken pox, too. Arthur is sad when Pal has to stay at the vet overnight for being sick. He blames D.W. for this, but when the vet tells him that Pal has been eating human food, he has to apologize to D.W. and learn what Pal is and is not supposed to eat.