When lightning strikes the school playground, Annie's dog loses her bark. After Mike's dog loses his bark as well, he and Annie decide to do some sleuthing. Searching for clues, they discover that the new school custodian, Mr. Duffy, is somehow involved in these strange events. Finally, Annie and Mike solve the terrible secret of the Graveyard Hounds-disembodied howls with the power to bring disaster on the entire town.