Solitary and dreamy, Blanche can run faster than anyone else, thanks to her exoskeleton legs. She spends endless hours contemplating the clouds, who seems to write signs in the Phoenix green sky. Lupianne, her older sister, thinks it is only a meteorological phenomena, an opinion shared by her father, much too anxious about the colony's air production center falling quotas. Only Sabian, a lonely painter, believes that there exists a link between the clouds signs and the ruins of an ancient destructed city, downstream from their own town.