Sacorra 6 is a conundrum, and Renata Colby loves puzzles. The top-ranking environmental scientist for the Council of Worlds seldom goes on project evaluations, but Sacorra 6 is intriguing enough to deserve her personal attention. Not even the most sophisticated scanner technology can track life-forms there. The cause of this so-called dissimulation effect has to be natural, since the Harimi who want to alter Sacorra 6 to their environmental liking are new arrivals and the planet has no native sentients.
Colby and her coxswain are traveling as guests when the Harimi-piloted shuttle crashes. With their hosts dead, the humans are rescued by descendants of Terran colonists who landed secretly several hundred years earlier. Only then does Colby learn that the Harimi's plan to "improve" this world will soon destroy it-and she has no way to escape, or let her own people know she's still alive, before that happens.