Harriet M. Welsch is a savvy spy. Every day, disguised in her foolproof spy outfit, the fearless sixth-grader travels her spy route, cannily observing the world around her and scribbling even the minutest detail into her secret spy notebook. Harriet (Michelle Trachtenberg) is determined to be a famous writer when she grows up, and Golly (Rosie O’Donnell), her companion and mentor, says that if Harriet is going to get a head start on her career she must write down everything that interests her — and everything interests Harriet! Her notebook is filled with candid and sometimes imaginary tales about her neighbors, her classmates, even her best friends, Janie and Sport.
But when Harriet’s classmates find her notebook and read its remarkable contents out loud, her life is turned upside down. In retaliation, the sixth-graders form a spycatchers club and turn the tables on Harriet. Even Janie and Sport join in!