"They're coming for us, from the sky and emptiness." Ten months ago, technology guru Sharon Mack and her autistic, strangely prescient daughter Bethany were trapped in the wild alternate version of Earth called Bear Country. They took refuge at Fort Eegan, an outpost built by a peculiar cult with mysterious ties to the US government. Now a new Exchange brings terrifying new consequences. The new Exchange blocks Fort Eegan's water supply, threatening deprivation now and catastrophic floods in the future. It also pits Fort Eegan against beings with superior technology, inhuman ruthlessness and a weapon capable of devouring everything in its path, including Fort Eegan. In spite of the danger from the new Exchange, the humans of Bear Country are nearing a war with one another. Ruthless escaped convicts hold hundreds of women hostage. With supplies dwindling, the convicts eye Fort Eegan's already limited resources. Inside and outside the fort, conflicts fester among the isolated humans, including a deadly love triangle. Fort Eegan's only hope is to unite before it is blown away by the devouring winds.