Louise Fitzhugh

Harriet M. Welsch is a spy. She's staked out a spy route, and she writes down everything about everyone she sees -- including her classmates and her best friends -- in her notebook. Then Harriet loses track of her notebook, and it ends up in the wrong hands. Before Harriet can stop them, her friends have read the always truthful, sometimes awful things she's written about each of them. Will Harriet find a way to put her life and her friendships back...

While at the beach for the summer, Harriet tries to uncover the author of mysterious religious notes that appear all over town, and which make her ponder her own beliefs, and Beth Ellen meets the mother she last saw when she was four years old.

Now "almost" twelve years old, Harriet tries to find out why her former nanny, Ole Golly, has returned to New York alone several months after getting married and moving to Canada.

While spying on her New York City neighborhood with a new friend, Annie, twelve-year-old Harriet decides that the only way to learn Annie's many secrets is to spy on her, as well.