The gang travels to Scotland to visit their friend Aggie McDuff and learn that her family castle is being haunted by the ghost of her great-grandfather Finnyan, using his bagpipes to lure in the Loch Ness Monster.
This episode includes examples of the following:
- Haunted Castle: McDuff Castle, haunted by the ghost of Finnyan McDuff.
- Hoist by His Own Petard: The ghost of Finnyan McDuff is literally snatched up by his own fake Loch Ness Monster, with Scooby using bagpipes to control it.
- Inflating Body Gag: In an attempt to play the bagpipes, Scooby blows them up like a balloon. The air briefly goes back into his own body before he reverts to his normal size.
- Ominous Fog: Plenty, and justified — the villain is using Loch Ness's natural fog as a cover for his actions.
- "Scooby-Doo" Hoax: The villain uses the ghost of Finnyan McDuff and the Loch Ness Monster to scare away the tourists who might otherwise catch on to his smuggling operation.
- Stock Ness Monster: The Loch Ness Monster, resembling a plesiosaurus but actually a mini-sub being used for transporting goods smuggled in from Switzerland.
