Tim Avery, an aspiring cartoonist, finds himself in a predicament when his dog stumbles upon the mask of Loki. Then after conceiving an infant son "born of the mask", he discovers just how looney child raising can be.

When a professor develops a vaccine that eliminates human allergies to dogs, he unwittingly upsets the fragile balance of power between cats and dogs and touches off an epic battle for pet supremacy. The fur flies as the feline faction, led by Mr. Tinkles, squares off against wide-eyed puppy Lou and his canine cohorts.