The Cat in the Hat made a return appearance in this 1958 sequel as a housekeeper. On this occasion, he leaves Thing One and Thing Two at home, but does bring along Little Cat A, nested inside his hat. Little Cat A doffs his hat to reveal Little Cat B, who in turn reveals C, and so on down to the microscopic Little Cat Z, who turns out to be the key to the plot. The crisis involves a pink bathtub ring and other pink residue left by the Cat after he snacks on a cake in the bathtub with the water running. Preliminary attempts to clean it up fail as they only spread the mess elsewhere, including a dress, the wall, a pair of ten dollar shoes, the bed, and then eventually outside where a "spot killing" war takes place between the mess, the Cat, Little Cats A through V, and an arsenal of primitive weapons including pop guns, bats, and a lawnmower. Unfortunately, the initial battle to rid the mess only makes it into an entire yard-covering spot. But then Little Cats V, W, X, and Y take off their hats to uncover microscopic Little Cat Z, who takes his hat off and unleashes a "Voom" which cleans up the back yard and puts all of the other Little Cats back into the Cat in the Hat's hat.