Willie the Weasel has created a formula that turns him into Mr. Hyde. While Blue Falcon and Dynomutt are on the trail of the mysterious Mr. Hyde, they encounter the Mystery Inc. gang and Scooby-Doo (who are unaware that Mr. Hyde is a supervillain and not one of their typical "spooks"). In The New Scooby-Doo Movies-fashion, they team-up with Blue Falcon and Dynomutt (who happens to be Scooby's hero) to stop Mr. Hyde, who has threatened to turn the population of the entire city into "Mr. Hydes" unless he is proclaimed mayor. Fred and the others find a clue (which turns out to be Willie the Weasel's glove), and Blue Falcon deduces that Willie is Mr. Hyde. Blue Falcon and Dynomutt have Mr. Hyde proclaimed mayor and pretend to turn themselves in so Mr. Hyde will lead them to his secret lair and trick him into showing them the antidote to the Hyde formula. Willie the Weasel and his canine partner-in-crime "Snitch" manage to escape. Blue Falcon and Dynomutt head to the Mayor's Mansion to stop Hyde from retrieving his stolen loot. The Mystery Inc. gang set up one of their infamous "Scooby Traps" while Blue Falcon and Dynomutt confront Mr. Hyde and Snitch. Dynomutt captures Snitch while Blue Falcon and the Mystery Inc. crew capture Willie the Weasel/Mr. Hyde. NOTE: This episode is a crossover between Dynomutt, Dog Wonder and Scooby-Doo.