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!

At the South Pole, the walruses install a rule of terror for the penguins. Tommy and his sister travel to the Equator, where legend says a jungle 'penguin warrior' and his six companions live, who can come rescue them. Tiger-striped bird 'tiger' Maurice is flattered and accepts the task. After recruiting gorilla Miguel, warthog Fred, frogs Bob and Al plus tarsier Gilbert, they set out. On the way they meet and recruit bat Batricia. After a long journey, they arrive in Antarctica and take on the giant bullies.