While traveling by plane to New York, Fourmille Gratule mysteriously falls into Ekhö, a parallel world that resembles Earth but functions without electricity, where dragons, fantastic creatures, and improbable technologies replace those of her own reality. Accompanied by Yuri, she inherits an artistic agency and gradually discovers the strange rules of this world dominated by the mysterious Preshauns. From city to city, Fourmille becomes involved in investigations, supernatural phenomena, and possessions that bring her closer to the secrets of Ekhö and the true nature of those who seem to control its balance.