Rital Madz had always viewed his cousin Den's obsession with recreating the powered flight of Ancient Humans as a waste of time and a good scientific mind. But their arguments must be set aside when an epidemic sweeps the continent, testing the fragile peace between Sime and Gen Territories that keeps both larities of humans alive. Trains stop running, factories close, and infected adolescents on both sides of the border die when their bodies undergo the strain of turning either Sime or Gen.

Rital leads the team desperately searching for an antidote to stem the epidemic, only to find that the only supply of a crucial ingredient lies on the other side of a river in flood stage. Suddenly Den's annoying hobby becomes the only means of transporting that ingredient And a single, untried young pilot must fly to retrieve it in an untested prototype, before the fabric of society unravels entirely.