Emily Wilde is a genius scholar of faerie folklore, and has catalogued many secrets of the Hidden Folk in her encyclopaedia with her infuriatingly charming fellow scholar, Wendell Bambleby, by her side.
But Bambleby is more than just a brilliant and unbearably handsome scholar. He's an exiled faerie king on the run from his murderous mother, in search of a door back to his realm. 
By lucky happenstance, Emily's new project, a map of the realms of faerie, will take them on an adventure to the picturesque Austrian Alps, where Emily believes they may find the door to Bambleby's realm, and the key to freeing him from his family's dark plans. 
But with new friendships for the prickly Emily to navigate and dangerous Folk lurking in every forest and hollow, Emily must unravel the mysterious workings of faerie doors, and of her own heart.