In the airborne nation of Astra, everyone learns to fly—on rowboats, gliders, chairs, or even umbrellas. But that is as much freedom as they have: they are kept in check by conservative, theocratic laws, under the purview of two kings who know more about pandering than progress.
No one has been more betrayed by the kings than Ruthenia Cendina. Her parents were executed for their heretical research, forcing her onto the streets for years until she found guardianship and employment under the inventor Titanio Calied.
Then a young goddess rises from the sea, wreaking meteorological havoc on Astra, and the kings find themselves forced to indecision by the very religious law that has been the bedrock of their governance. In the wake of this disaster, Ruthenia soon finds herself involved in an underground project far more heretical than her parents'.