Spring has sprung, and with it, a full line-up of programming at Larkspur Community Library. Director Greta Plank is preparing to host the Wisconsin Library Organization's annual conference—and dreading the arrival of her ex-boyfriend—while also helping a local treasure-hunting club coordinate a showcase highlighting Northern Wisconsin's gangster trail and the nearby hideouts of the notorious criminals of the early twentieth century.



When Greta overhears the library board president and a member of the treasure-hunting club arguing about a secret discovery, her curiosity is piqued—even more so when one of the women leaves a book with a sequence of strange markings on its pages in the library book return bin. Before Greta can ask about the marginalia, the book's outspoken owner turns up dead.



At the request of the police—though against the better judgment of her beau, Detective Mark McHenry—Greta sets to work trying to decipher the peculiar notations, and she quickly hypothesizes that there's more to the story. Greta must work against the clock to decode the dead woman's book code. What she finds is someone willing to go to great lengths to keep a secret buried in the stacks—and the past—even if it means killing again.