Harriet the Spy, Double Agent (Harriet the Spy Adventures, #2)

Harriet is impressed to learn that the girl she has befriended, now called Annie Smith, is the person who not only created three names–Rosarita Sauvage, Yolanda Montezuma, and Zoe Carpaccio–but also three distinct personalities to match. This girl has potential. Being a spy has always been rather solitary, so Harriet is glad to have a new friend and spy partner. But then Harriet realizes that Annie reveals very little about herself, and indeed, is not telling the truth about where she goes and who she meets on the weekend. Sport says he’s in love with the girl, but Annie lets drop she’s in love with an older man. Harriet can’t understand anything at all about this thing called love–even when she asks Ole Golly for advice, she still wonders. But as Harriet unravels Annie’s mystery, she comes to appreciate the many different kinds of love there are.