Unconventional Annie, Natalie’s new neighbor, is quite different from Natalie’s polite private-school friends and her untidy house a contrast to Natalie’s ordered one. Her idea of starting a secret-collecting club is downright compelling, however, as is the notion of adopting code names. Olive (Natalie) and Elvis (Annie) spy on their neighbors throughout the summer, gathering hidden bits of information about nearly everyone and creating a gallery of secrets on notecards in the space under Annie’s porch. Somewhere behind the boldness, Annie harbors a secret sadness that Natalie can’t quite fathom—until she learns the truth about Annie’s mother. The collapse of the girls’ friendship, along with their secrets project, devastates them both until a kindly neighbor helps to reunite them. Watson has penned a satisfying friendship story with drama and humor in fine balance. (Fiction. 9-12)