Jack and Jilly Doone are twelve-year-old twins bound by blood and forbidden secrets. Running wild through endless August afternoons, they explore the tributaries of Chesapeake Bay, spinning fantasies and sneaking cigarettes. But when a near-drowning awakens a strange power in Jack, the line between fantasy and reality blurs....

Kestrel is an airie, one of five mutant races born in the conflict known as the Viral Wars. With one companion from each of the other races—a delph, a merm, a mander, and a boggle—he sets out to battle human enemies sworn to exterminate mutantkind.

Now the destinies of two worlds move toward a shocking convergence ... and a climax of violent transfiguration.