The surreal glow of the aurora borealis illuminates the sub-Arctic sky but provides no warmth for the ground below. Despite temperatures that can plunge to 60 degrees below zero, there is life in the dark, frigid wilderness. Wolves prowl in search of prey while underground an Arctic squirrel hibernates, embracing the cold by lowering its body temperature to near freezing. He must labor back to a groggy consciousness every few weeks to survive. A grizzly mother exists in a kind of twilight sleep for the winter, her reveries interrupted by the needs of her infant cubs. Between nursing her young and a winter's fast, she may drop 100 pounds. With neither fur nor warm blood for protection, a wood frog lies frozen solid on an ice cube. Its body would shatter if it could be moved by the life within.
Back outside, the deep snows slow the movement of a foraging moose and her young calf. A fallen caribou testifies to winter's rigors, but its misfortune becomes a windfall for an ermine, a wily weasel that uses the carcass as a source of food and shelter.
The winter equinox in March brings more light if not appreciably more warmth to Denali. The ground squirrel peaks out to the unfamiliar sound of a dog sled driven by biologist Carol McIntyre, who braves the inhospitable landscape to conduct research on the area's gold eagles.