After Mystery, Inc. solves the mystery of the Luna Ghost at a toy factory, long-brewing friction between Fred, the self-obsessed glory hog; Daphne, who has become sick of being the damsel in distress; and Velma, from whom Fred regularly steals credit for her plans, causes the gang to break into a heated argument and subsequently disband, abandoning a dismayed Scooby-Doo and Shaggy, leaving them to care for the gang’s van, the Mystery Machine.
Two years later, they are all invited to solve a mystery on a horror-themed tropical resort named “Spooky Island” at the behest of owner Emile Mondavarious, who believes the guests have fallen under a demonic curse. While Shaggy and Scooby hope this will bring the gang back together, Velma, Fred, and Daphne each intend to solve the mystery on their own. Velma attends a ritualistic performance given by actor N’Goo Tuana and his henchman, famous luchador Zarkos.
N’Goo claims ancient demons once ruled the island, but have been plotting revenge ever since they were displaced by the resort. Meanwhile, Shaggy falls for a girl named Mary Jane, who is allergic to dogs, distancing himself from Scooby in the process.
The gang members are led separately to the resort’s haunted house ride, and they decide to get along for the time being to split up and search for clues. Fred and Velma discover a film that educates inhuman creatures about human culture, while Daphne finds a pyramid-shaped artifact called the “Daemon Ritus”.
Later, at the resort’s hotel, Fred, Velma, and Mondavarious are kidnapped and possessed by the island’s demons. Mary Jane calls the Coast Guard for help but ignores them. The next day, after trying and failing to tell Shaggy that Mary Jane is secretly possessed by a demon, the two have a falling-out that results in Scooby-Doo going missing as well; Zarkos steals back the Daemon Ritus from Daphne, who is also captured and possessed.
Shaggy searches for his friends underground and finds a vat of protoplasm containing the souls of all those possessed. He frees the souls of Daphne, Fred, and Velma, who quickly discover sunlight destroys the demons. A local voodoo priest informs the gang the demons are to perform their “Darpokalypse” Ritual, which will see them rule the world for 10,000 years if a pure soul is sacrificed in the Daemon Ritus.
The gang infiltrates the ritual, where Mondavarious is foiled in sacrificing Scooby’s soul by Shaggy. Mondavarious turns out to be a robot controlled by Scooby’s estranged nephew Scrappy-Doo, who has been plotting revenge on the gang for being abandoned long ago due to his increasingly power-hungry and egomaniacal nature.
With a thrilling showdown, Mystery, Inc. saves the day, defeats the demons, and reunites to continue solving mysteries. Don’t miss out on the action-packed adventure of Scoob! Watch Free now!