Scooby Doo; Shaggy; Velma; Daphne; Fred; Chief Klein; Mr. Brewster; a thug named Mike
Police chief Klein receives a medal of honor from the Businessmen Association for cracking down on phony gypsy fortune-tellers. A gypsy appears and curses the chief saying that upon moonlight he will destroy the town. Mr. Brewster, an art dealer, throws a party that evening at his home but feeling ill Chief Klein goes upstairs to lie down. A snarling monster later appears wearing the chief's clothing. The gang is suspicious that the chief is being framed for crimes he did not commit and set out to prove Brewster is behind the monster's rampage.