In the gripping third volume of Christelle Dabos's best-selling saga, Ophelia, the mirror-travelling heroine, finds herself in the magical city 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 is finally time to act, to put what she has discovered in the Book of Faruk to good use. Under an assumed identity she travels to Babel, a cosmopolitan and thoroughly modern ark that is the jewel of the universe, and where automata have taken over the most humble jobs from humans. But under the surface of this pacific and orderly ark social unrest stirs, fed by the memories of a fateful purge long ago, and the inhabitants' growing fear of being replaced altogether. Will Ophelia's talent as a reader suffice to avoid her being lured into a deadly trap by her ever more fearful adversaries? Will she ever see Thorn, her betrothed, again?