On a rainy day, two siblings, Sally and her brother, are stuck indoors with nothing to do. Their mother is out, leaving them alone and bored within the confines of their home. Suddenly, a flamboyant and mischievous cat wearing a tall striped hat appears, bringing with him chaos and excitement. He introduces them to a world of fun and trouble, determined to lighten up their dreary day. Despite the children's initial hesitation, the Cat's charismatic and unruly antics soon draw them in. The house quickly transforms into a playground of imaginative escapades, featuring an array of zany tricks and stunts that defy the mundane.

Not long after, the Cat's activities escalate in unpredictability, stirring anxiety within the kids. The situation grows more intense with the arrival of Thing 1 and Thing 2, two energetic creatures who amplify the disorder. The children become increasingly concerned about the mess being created and the consequence they might face once their mother returns. Amidst the escalating chaos, the siblings' fish, acting as a voice of reason, warns them about the looming trouble. The day spirals into a whirlwind of excitement and tension as the children try to manage the pandemonium that threatens to engulf their once-peaceful home.