Human colonists have terraformed the planet Lithia, but now the green biosphere is unraveling. In its place is the old Lithia, toxic to some, preferable to others, including the orthong. Aliens. Monsters, some say.

Finding himself marooned on Lithia, young Reeve Calder is determined to make a home--even rebuild the planet. But he is a newcomer, soon to encounter the powerful forces already embedded in the transforming ecology.

There are the savage colonists, inhabiting the ruins of vanished power. There are the Somaformers, a doomsday cult tampering with adaptive genes. There is Loon, a feral girl who leads the marooned group by her mad, internal compass. There is Nerys, a young woman enslaved by the orthong, and determined to rise in their ranks.

Driven by a whispered clue from a dying man, Reeve and his companions must reach the great rift valley where the final reckoning awaits, one that will decide world dominance--or an unthinkable world cataclysm.