In the hot, gossipy town of Stony Lonesome, shy eleven-year old Willa interacts with others the only way that feels right to her—the mail. She loves the mail so much that she hopes to become a mail carrier herself one day. But her dreams of delivering birthday cards, thank-you notes, and love letters come crashing down when she’s mistaken for the notorious Two Gum Tilly, a bandit rumored to be stealing mail for as long as folks can recall.

Now an outlaw herself, Willa realizes the only way to clear her name is to bring the real crook to justice. But when a chance encounter introduces her to the Gumshoe Gang, a group of runaways looking to right the wrongs of the letter-looting thief, she finds that human connection might be her only path to freedom. Can Willa clear her name and revive her dreams of postal glory, or has she stamped her last letter . . . forever?