TRICK OR TRAP?! Mystery Inc. just cracked the biggest case of all! Scooby-Doo and his pals have tracked down Coco Diablo, the head of the notorious costumed crime syndicate that includes the Black Knight, Space Kook and the Ghost Diver. With Coco and her kitty in prison, the gang can finally enjoy a break, right? Wrong! Menacing dopplegangers and classic foes show up in Coolsville, threatening Hallowwen, so it's up to the meddling kids and their unliekly new partner to unmask the latest scoundrel. With trick-or-treat on the line, it's gotten personel for Scoob and Shaggy!