Sixth-grader Harriet attends school on the New York`s Upper East Side along with her two best pals, Sport and Janie. After school every day, she takes her notebook and proceeds through her spy route. Harriet observes the rich lady who never gets out of bed; the man with twenty-five cats and the Italian family who runs a grocery store. She writes brutally honest notes on them all. Harriet`s downfall is that she also writes notes about people she actually knows…After a game in the park when her notebook is knocked out of her hands and read by her classmates, Harriet`s innermost thoughts are revealed and she is shunned by all her classmates, who form the Spycatcher`s Club. After her parents find out what`s happened, Harriet receives a final, crushing blow. She is no longer allowed to take notes — her parents, her teacher and even the cook search her every day for a contraband notebook. Harriet`s only consolation is the love and the wise advice of her nanny who manages to get her through this difficult period in her life.