Dr. Viper floods Megakat City with Katalyst X-63, a ""hideous mutating ooze"" that turns normal animals into giant monsters. With the city submerged in slime and infested by huge, repulsive mutants, the Swat Kats must undertake a perilous mission to Megakat Biochemical Labs, where they must retrieve the antimutagens needed to restore everything to normal. T-Bone, who can't swim, nearly drowns in the slime, and later becomes a mutant himself when one of the creatures bites him. Worse, Dr. Viper eventually uses the katalyst on himself, turning into a skyscraper-sized monstrosity.
