In this third volume of the Christelle Dabos's bestselling saga, Ophelia, the mirror-traveling heroine, finds herself on the ark of Babel guarding a secret that may provide a key both to the past and the future. After two years and seven months biding her time on Anima, her home ark, it's finally time to act, to put what she has discovered in the Book of Farouk to use. Under an assumed identity she travels to Babel, a cosmopolitan and thoroughly modern ark that is the jewel of the universe. Will Ophelia's talent as a reader suffice to avoid being lured into a deadly trap by her ever more fearful adversaries? Will she ever see Thorn, her betrothed, again?