David De Kat is an environmental activist who dressed as a cat takes on local industrialist Oskar Dias, who threatens nature with his company Af-Val. Especially Dias' daughter Helena takes the fight against the Cat very seriously. It is true that De Kat always takes care of her goons, which invariably consist of not too bright people. The Cat eventually gets the help of Dias's wife Nellie and also of Dias's niece, Andrea. He coordinates his actions from the Belmont mansion and has a blue Volkswagen bus with a white roof at his disposal.