Two contrasting worlds of fire and ice - rugged, high snow-capped mountains in the depths of winter, and Death Valley, the hottest, driest place in North America - are some of the harshest environments on Earth. This episode includes: deadly avalanches that sweep climbers and skiers off the slopes in Utah, destroy a town in France, and send a passenger train plunging down a cliff into a river in Washington; the mysterious sliding rocks at Death Valley's Racetrack Playa; and some people who risk their lives to work and play in the extremes.