Winter in Yellowstone. Driving snow and temperatures 50 degrees below zero collide with spewing heat from subterranean forces, creating dramatic, otherworldly displays. Host Bill Pullman embarks on a journey over vast blankets of snow, through sparkling prisms of "diamond dust," and across rivers warmed by geothermal springs. Marvel at the park's wildlife and see how the area's extreme conditions pose challenges even for animals that have evolved to survive its winters.