At the grand opening of the Coolsville Museum, the Evil Masked Figure releases the recreated Pterodactyl Ghost. The Mystery Inc. 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.