Harriet is an 11-year-old girl who favors wearing old jeans and a tool belt to hold her spy gear. She was born into a privileged existence among the wealthy families of the Upper East Side in New York City. She doesn’t have a particularly close relationship with her parents because her needs are met by the family cook and her live-in nanny. She aspires to be a spy when she grows up and spends most of her time recording her observations in notebooks about people in the neighborhood.

While Harriet is keenly observant and ingenious in finding ways to watch people without being seen, she is frequently judgmental and unkind in her comments about them. This tendency nearly destroys her relationship with her two closest friends when they accidentally read what she wrote about them in her journal. Harriet’s only real parental figure is her nanny. When Ole Golly leaves, Harriet has difficulty navigating the tricky world of human interaction. Fortunately, Ole Golly finally sends her some advice about how to channel her writing abilities constructively and repair her damaged relationship with her friends.