When Works Progress Administration (WPA) editor Millie Lang finds herself on the wrong end of a potential political scandal, she’s shipped off to Montana to work on the state’s American Guide Series—travel books intended to put the nation’s destitute writers to work.

Millie arrives to an eclectic staff claiming their missed deadlines are due to sabotage, possibly from the state’s powerful Copper Kings who don’t want their long and bloody history with union organizers aired for the rest of the country to read. But Millie begins to suspect that the answer might instead lie with the town’s mysterious librarian, Alice Monroe.

In a dual timeline that reaches back more than a decade earlier, Alice Monroe created the Boxcar Library in order to deliver books to isolated mining towns where men longed for entertainment and connection. Alice thought she found the perfect librarian to staff the train car in Colette Durand, a miner’s daughter with a shotgun and too many secrets behind her eyes.

Now, no one in Missoula will tell Millie why both Alice and Colette went out on the inaugural journey of the Boxcar Library, but only Alice returned. The three women’s stories dramatically converge in the search to uncover what someone is so desperately trying to hide: what happened to Colette Durand.