Harriet (Michelle Trachtenberg) is an 11-year-old sixth grader and a spy/writer who is best friends with Simon Rocque (Gregory Smith) and Janie Gibbs (Vanessa Chester). She lives a privileged life with her parents and her nanny, Golly (Rosie O'Donnell) who's the only person who knows all the things that Harriet has been snooping on. Harriet and her friends are enemies with mainly Marion Hawthorne (Charlotte Sullivan). For awhile, Harriet lives life very well with being a spy and having fun with Golly.