On a rainy day, two siblings—Sally and her brother—are stuck indoors with nothing to do. Their boredom is interrupted by the unexpected arrival of the mischievous Cat in the Hat, who brings chaos and fun into their home. Despite the protests of their pet fish, the Cat introduces them to his troublemaking companions, Thing 1 and Thing 2. Together, they engage in a series of wild antics that turn the house upside down. Just before their mother returns, the Cat cleans up the mess, leaving no trace of the day's mischief.