| Director | Spike Brandt, Tony Cervone |
|---|
Fred, Daphne, Velma, Shaggy and Scooby-Doo travel to an amusement park called Kiss World to see Kiss at their big Halloween concert and solve a mystery, mostly because Daphne has a crush on Starchild (Paul Stanley), much to Fred's annoyance. However, when the gang arrive, security chief and former government defense employee Delilah Domino refuse to let them in due to unexplained reasons, but they sneak in anyway, only to be caught by Delilah, who bans them from Kiss World. At that moment, Kiss arrives, and after the gang explains they just want to help, they tell Delilah the kids are free to stay, to which she reluctantly agrees, though she does not trust them just because they are amateur detectives and that she is watching them. The Demon (Gene Simmons) initially opposes the idea due to Scooby accidentally spraying a water gun on him when he came to Shaggy and Scooby for a surprise visit, but later relents. As the gang split up for clues, Shaggy and Scooby are chased by an entity until Kiss comes to pull them out of harm's way. They tell the gang the entity is called the Crimson Witch, and she has been terrorizing the park for a while, and they need her to disappear before the concert. Meanwhile, Delilah threatens to hold park owner Manny Goldman accountable before a local town council for property damage caused in Kiss World by the Crimson Witch if he doesn't close down the park for safety's sake.
A strange, perpetually barefoot fortune-teller named Chikara says the witch is from an alternate universe called Kissteria and plans to use the Black Diamond Kiss uses in their hit song "Detroit Rock City" to summon a monster called The Destroyer to conquer the Earth, which Velma finds hard to believe. To stop the Crimson Witch, the gang uses the diamond to lure the witch. However, the Crimson Witch chases them through a portal to Kissteria. She manages to steal the diamond and unleash The Destroyer, but the gang and Kiss arrive in a spaceship to stop the monster. The gang then returns to Earth, where they wake up believing the witch's gas caused them all to have a hallucination. They unmask the Crimson Witch as Delilah, who not only wished to sell the Black Diamond (needed for laser technology) to a competing defense company as revenge against her former employers, but to also prevent Mystery Inc. from entering Kiss World by disguising herself as a security guard in fear of them trying to expose her plot. Defeated, Delilah is carted off to jail for her crimes against the park and its staff.
Later, the Starchild kisses Daphne right in front of Fred. Daphne then kisses Fred on the cheek, much to his delight. The Demon gives Shaggy and Scooby a smile. Shaggy and Scooby then see Kiss fly away with the Black Diamond to present it to the Smithsonian Institution. Shaggy asks Scooby if they should tell Velma regarding the uneasiest case Mystery Inc. has ever solved in their entire lives. However, Scooby suggests they do not, simply stating: "Why rock her world?"