Humans have lived on Tofarn, planet of creeks and rivers, for seventy years, but they still don't understand the Tofa. The Tofa are an enigma, from their featureless faces to the four arms that sometimes seem to be five. They take arbitrary umbrage at the simplest human activities, while annoying their human neighbors in seemingly pointless ways. The next infuriating, inexplicable incident may explode into war.
Scientist Mara Cadell's radical proposal: that host mothers carry fraternal twins, human and Tofa, in the hope that the bond between twins can bridge the gap between species. Mara knows about the bond between twins: her own twin, Levi, died in utero, but she has secretly kept him alive in her mind as companion and collaborator.
Mara succeeds in obtaining governmental backing for her project – but both the human and Tofa establishments have their own agendas. Mara must shepherd the Twin-Bred through dangers she anticipated and others that even the canny Levi could not foresee. Will the Twin-Bred bring peace, war, or something else entirely?