Twelve-year-old Sebastian is struck by the eerie similarity of photos separated by half a century and half the globe. The photos are of Gandhi and Dr. Martin Luther King Jr., but to the side in all of them is a mysterious boy holding a book to his chest, the same book in every photo. It is too strange to be a coincidence, but what else could it possibly be? Back home in Virginia, seventh graders Henrietta and TP discover a novel that changes each time Henrietta reads it. When Sebastian learns that a girl his age has the book, he needs to find her. Figuring out the powerful mystery of Unus Operor, the magical book that seems to have the answers to all their questions involves saving Henrietta and TP'-s school library, tracking down a famous author, creating beautiful graffiti in the school bathroom, and forming a meaningful new friendship.