Scooby-Doo, Shaggy and the crew travel to Scotland on vacation and find themselves unexpectedly tackling their biggest monstrosity ever: the Loch Ness Monster. Does it really exist? Early evidence suggest that the monster does indeed exist, but when something gigantic appears outside a window of Daphne's ancestral family castle, it's up to Scooby-Doo and the crew to solve one of history's longest-running mysteries.