Moon Over Manifest

 Vanderpool, C. Moon over Manifest. (2010). New York: Random House.

Abilene Tucker feels abandoned. Her father has put her on a train, sending her off to live with an old friend for the summer while he works a railroad job. Armed only with a few possessions and her list of universals, Abilene jumps off the train in Manifest, Kansas, aiming to learn about the boy her father once was.
Having heard stories about Manifest, Abilene is disappointed to find that it’s just a dried-up, worn-out old town. But her disappointment quickly turns to excitement when she discovers a hidden cigar box full of mementos, including some old letters that mention a spy known as the Rattler. These mysterious letters send Abilene and her new friends, Lettie and Ruthanne, on an honest-to-goodness spy hunt, even though they are warned to “Leave Well Enough Alone.”