While Professor Brody tries to create a serum to cure dog allergies in humans, the cats try to have this serum. The dog Lou, who's adopted by the Brody family, tries to stop the cats' evil plans to take over the world led by a cat named Mr. Tinkles.
Cats and dogs are forced to set aside their ancient feud, to face a common enemy that threatens to destroy their world.
After the peace between cats and dogs leads to the birth of a secret organization tasked with protecting the world, an evil parrot seeks to break up the peace and send cats and dogs after each other again.