Brother and sister Conrad and Sally often stay at home on their own. Their mom Joan is constantly busy at work. She brings up the children alone and tries to arrange her personal life. One rainy and gloomy day, the cat in the hat comes to the kids` house and begins to entertain them in every possible way. Playing around, the heroes do not notice that they turned everything upside down, and the frantic cat has to disappear before their mum`s arrival.