Holly Black says that she and co-author Tony DiTerlizzi received a letter from Mallory Grace on behalf of Mallory and her siblings, Jared and Simon. The letter accompanies a photocopy of a page from a strange book that describes faeries as real. Mallory asks that Black and DiTerlizzi help the kids get the book to a publisher.

The authors reply and soon receive a package containing the book, followed by a visit from the three children. The authors become involved in the children’s story and believe it’s important: “There is an invisible world around us and we hope that you, dear reader, will open your eyes to it” (viii).

In her letter, titled “Letter from the Grace Kids,” Mallory Grace writes: “The book tells people how to identify faeries and how to protect themselves” (ix). The children will forward the book manually to the authors because regular mail is “too dangerous.” They want the world to know that what happened to them “could happen to anyone” (ix).

To the Grace children, their new home, an old Victorian mansion, looks like a bunch of shacks piled atop one another. A few flecks of paint still remain on the rundown building.