When editor Millie Lang finds herself on the wrong end of a political scandal, she’s shipped off to Montana to work on the state’s American Guide Series. Millie arrives to an eclectic staff claiming their missed deadlines are due to sabotage, possibly from the state’s powerful Copper Kings. But Millie begins to suspect that the answer might instead lie with the town’s mysterious librarian, Alice Monroe. More than a decade earlier, Alice Monroe created the Boxcar Library in order to deliver books to isolated mining towns. Alice thought she found the perfect librarian in Colette Durand. 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.