When a group of monsters are unleashed on Coolsville, Scooby-Doo and his friends must solve the mystery and save the town from chaos. With their detective skills and courage, they face off against the monsters, uncovering a plot to wreak havoc on their beloved city.

After an acrimonious break up, the Mystery Inc. gang are individually brought to an island resort to investigate strange goings on. Two years later, they reform to solve a mystery on Spooky Island, a horror-themed tropical resort owned by Emile Mondavarious. The gang discovers that ancient demons are plotting revenge and have possessed some of the island's inhabitants, including Fred, Velma, and Mondavarious. With the help of a voodoo priest, they devise a plan to trap the demon cult and save the world from their rule. In the end, they defeat the demons and vow to continue solving mysteries together.