Tumbling After - Paul Witcover - Bog

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.