Scooby-Doo and Shaggy must go into the underworld ruled by the Goblin King in order to stop a mortal named The Amazing Krudsky who wants power and is a threat to their pals, Fred, Velma and Daphne.
Mystery Inc. has cracked the case to top all cases! They’ve tracked down Coco Diablo, the head of a notorious costume crime syndicate. With Coco and her kitty in prison, Mystery Inc. thinks that they can finally enjoy a break. Wrong! Suddenly, menacing doppelgänger ghosts of the Scooby crew and favorite classic foes show up in Coolsville to threaten Halloween. Now it’s up to the meddling kids to unmask the latest scoundrel and save Halloween!
Join Scooby-Doo, Shaggy and the Mystery Inc. crew as they head to Chicago for Talent Star, a hit talent show in which Fred and Daphne are finalists with some high hopes. Unlucky for them, the competition is frightful as the show is being broadcast from an opera house with a history of horrors and a particularly vengeful phantom that has cursed the show's production.
As the ponies prepare for another Hearth's Warming, families come together to celebrate the holiday; Pinkie Pie, Fluttershy, Applejack, Rarity, and Rainbow Dash are ready for the big day, but Princess Twilight Sparkle doesn't have time to celebrate.