Scooby-Doo! and the Loch Ness Monster
Chillman came to Drumnadrochit in his van because he had heard about the new evidence of the reality of the Loch Ness Monster: the damage it did around the Blake Castle and the footprints it left. That damage was done by a land-going robot operated by the Haggart bros., hired by Prof. Fiona Pembrooke.
Later, Pembrooke hired the same two brothers to steal Chillman's van and disguise it as a second land-going version of the Loch Ness Monster. She also had a water-going version (a disguised submarine).