The members of Mystery, Inc. join with the Three Stooges to thwart the ghost of the Red Baron, a daring evildoer who has scared away all of farmer Sawyer's crop-dusting pilots in an effort to pressure Sawyer into leaving his land.

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.