When interstellar civil war erupts, human colonists are marooned on the nearest world that's habitable—and just barely that. Ill prepared for the two-plus-year winters, they must adapt what they have to be what they need, including their attitudes when they find the planet inhabited by intelligent life living in lava-warmed caves. A double book, in the Ace-double style, combined with Exile on Vlahil by Ardath Mayhar.