takes place in a post steampunk world where dark matter and dark energy have been harnessed by a reclusive genius known as "Father Inventor" - revered by many, reviled by more. Energy problems solved, humanity is obsessed with unlocking the secrets to eternal life. Unrestricted experimentation has produced a population of parentless and deformed children, the Darling Undesirables. Named for their missing body part, each is pampered and indulged. The most adored , 15-year-old Heart, dreams of escaping with her friend, Eye, and the beloved, centuries-old, clockwork horse. But first, she must save Father Inventor and the world he brought into being from the evil forces of The Purists.