Every fifteen years, Saturn eclipses the sun, and Titan spends seventy-two hours in darkness. Nine months into the Vicks' stay, four Titanian days before the eclipse is due, an ice mountain near the Vicks' shack collapses. The Vicks escape the destruction of their shack, but find themselves stranded a hundred miles from the main human settlement on Titan, the United States-ran Nivia, otherwise known as the City of Snow, on the far side of the Mountains of the Damned. Tim Vick decides that they should try to reach Nivia, since the wind recently shifted and will be at their backs for the next eight days.