The lovable, easily frightened Great Dane, Scooby-Doo, returns to the big-screen when Scooby and the Mystery, Inc. sleuths confront an anonymous masked villain plotting to take over the city of Coolsville using a monster machine that creates Mystery Inc.'s classic foes such as The Pterodactyl Ghost, The Black Knight Ghost and The 10,000 Volt Ghost. Meanwhile, the gang's detecting abilities are scrutinized by relentless reporter Heather Jasper-Howe (Alicia Silverstone), aided by museum curator Patrick Wisely (Seth Green) and thwarted by nasty Jeremiah Wickles (Peter Boyle).