For Kat Greene, life is messy at school – and at home. Kat lives in New York City and attends fifth grade in the very progressive Village Humanity School. At the moment she has three major problems—dealing with her boy-crazy best friend, partnering with the overzealous Sam in the class production of Harriet the Spy, and coping with her mother’s preoccupation with cleanliness, a symptom of her worsening obsessive-compulsive disorder.
Her boy-crazy best friend Halle thinks Kat is trying to steal her crush and stops talking to her. Kat is assigned a lame role in the fifth-grade production of Harriet the Spy, even though she’s perfect for the role of Harriet. Her divorced mother is struggling with obsessive-compulsive disorder and the need to clean constantly, scrubbing the kitchen floor with a toothbrush and bleaching Kat’s underwear.
Things go from bad to worse when Kat’s mother decides to become a contestant on Clean Sweep, a game show about cleaning. Kat can’t tell her dad about Mom’s obsessive washing, scrubbing, and organizing – she doesn’t want to have to move uptown with him and his new family. The more her mom’s cleaning interferes with their lives, the more Kat worries. She knows she should talk to her mom, but she’s afraid.
With nowhere to turn, Kat reaches out to the free-spirited psychologist, Olympia, at her new-age private school in New York’s Greenwich Village. Olympia encourages Kat to be honest, and Kat finds a way to finally reach her mom, make up with her best friend, and excel in the school play. Eventually, Kat realizes that sometimes asking for help is the best way to clean up life’s messes.