Mr. Hyde, alias Willie The Weasel, abetted by Hyde Dog, demands to be mayor of Big City, threatening its citizens with a sinister formula that turns them into evil Hyde-like creatures. Blue Falcon and Dog Wonder, assisted by the Scooby-Doo detectives, plan to trap the wily Mr. Hyde and agree to his request. Once this results, Mr. Hyde, via his terrible greed, is snared into a wild falcon fracus: Dynomutt captures Hyde Dog and the antidote that will save Big City, with Blue Falcon's Falconclaw scooping up the fleeing Willie The Weasel, b.k.a. Mr. Hyde. After being commended by the Mayor, Dynomutt, executing a heroic exit from City Hall, accidentally gets caught in one of Shaggy's Scooby-traps!