The gang must prove that a ghostly horseman haunting Hagglethorn Castle is a fake apparition. Otherwise, Davy Jones' uncle will have to sell the Scottish fortress, once a thriving tourist spot, to the greedy Duke of Strathmore.

Scooby and Mystery Inc. meet the terrible twosome--Penguin and Joker--on a camping trip in the forest. To stop the evildoers, the kids enlist the aid of those crusaders against crime, Batman & Robin.