When Mystery, Inc. are guests of honor at the grand opening of the Coolsville Museum of Criminology, a masked villain shows up and creates havoc before stealing the costumes of the gang's most notorious villains: Black Knight Ghost, Pterodactyl Ghost and Tar Monster. Could it be that their nemesis, mad scientist Jonathan Jacobo has returned and is trying to recreate their deadliest enemies? Velma has a crush on the museum curator Patrick Wisely despite her fears of intimacy but why is he acting so suspicious? The Mystery Gang is hard pressed to succeed this time, since annoying television reporter Heather Jasper-Howe insists they are buffoons.
The Mystery Inc. gang must save Coolsville from an attack of past unmasked monsters brought to life by an evil masked figure trying to "unmask" the gang.
- In Scooby-Doo 2: Monsters Unleashed, the teenage detectives of Mystery Inc., Fred (Freddie Prinze Jr.), Daphne (Sarah Michelle Gellar), Velma (Linda Cardellini) & Shaggy (Matthew Lillard), must fight their former antagonist that are brought back to life by a new nemesis, the Evil Masked Figure. At the grand opening of the Coolsville Museum, the Evil Masked Figure releases the recreated Pterodactyl Ghost (flying reptile). The gang tries to capture the reptile, but it flies out the window with the Evil Masked Figure in tow, because Shaggy and Scooby forget to tie the rope. The gang embarks on an investigation of how this reptile came to life. Shaggy and Scooby go on their own to prove that they are real detectives and not mess-ups. The gang discovers that the Evil Masked Figure has built a machine that was used to regenerate the reptile, and he is about to bring back other monsters such as the Black Knight, Captain Cutler's Ghost, and the 10,000 Volt Ghost. The Evil Masked Figure wants to destroy the reputations of the detectives at Mystery Inc. and take over Coolsville. Douglas Young (the-movie-guy)