The kids head to Hillside High, to help Daphne's cousin Jennifer out. It seems that a creature from the chemistry lab has been scaring off students and forced the school to cancel its dance. Does it have something to do with Professor Marsden, who believes kids should do school work and have no fun, or someone else? / The gang goes to Blake Manor for a vacation, and gets there in time for the costume party, where Mr. Blake will be auctioning off a valuable stamp worth millions. But there is a cat burglar, the Masked Manx, on the loose, who leaves an ace of spades in the place of every item he steals. Can the kids stop him and save the stamp?