D.W. gets poison ivy while playing a game with Arthur and Buster and is worried about being teased by her classmates, so Buster tells a story about how he got asthma. When Buster learns that he has asthma, his friends start treating him differently, with Arthur scared that any dust could affect him, while Francine believes it is a contagious disease. Buster explains that he educated his friends by doing a science project about asthma, which helps D.W. feel better. Muffy and Francine play several pranks on Arthur, Buster, Binky, and Brain and invite them to a Halloween costume party at a haunted house. The boys get revenge on the girls at the party, but their pranks get unknowingly interrupted by real ghosts.