Following the events of the first film, Fred, Daphne, Velma, Shaggy and Scooby-Doo attend the opening of an exhibition at the Coolsonian Criminology Museum commemorating their past solved cases with monster costumes on display. However, the celebrations are interrupted by a masked man known as the Evil Masked Figure who steals two costumes using the reanimated Pterodactyl Ghost. The gang are ridiculed by journalist Heather Jasper Howe, who starts a smear campaign against them. Concluding an old enemy is the mastermind, the gang revisit old cases, dismissing the former Pterodactyl Ghost, Jonathan Jacobo, due to his death during a failed prison escape three years ago, they guess that Jeremiah Wickles, the Black Knight Ghost's portrayer and Jacobo's cell mate in prison, is the culprit.