Twelve-year-old Rosie Oakes' mother misses everything that makes mothers love their daughters. All her life, Rosie has known this and turned to stories for comfort. Then, on the night Rosie decides to give up her stories forever, an unseen ally helps her discover The Witch Hunter's Guide to the Cosmos, a book that claims that all evil in the world stems from thirteen invisible witches... but they cannot be stopped. One of these witches—the Memory Stealer—possesses a hidden power to steal our most precious treasures: our memories. And it is this witch who has cursed Rosie's mother.

In her quest to save her mother—with her loyal friend Germ by her side—Rosie will find the hidden layers beneath the reality only she thought she knew: where ghosts linger like shadows from the past, where clouds bear witness to the world, and where a ladder hangs from the moon leading to something greater and grander. Here, words are weapons against the darkness, and witch hunters are those brave enough to unleash their imagination in the face of the unbelievable. The knowledge of her beloved stories is an arsenal in this world, but to unleash its power, Rosie must dare to hold on to hope and believe in herself in the face of overwhelming odds. But can one girl truly hope to undo forces that have been at work for centuries?