Half a million tons of snow travelling at up to 200 miles an hour... From the Andes to the Alps, ever since man made his home beneath the mountain, avalanches have preyed on him. But now the careless tourist is replacing the mountain dweller as the avalanche's main victim. This film looks at avalanches from their beautiful beginning in the snow crystal to their terrible effect on the dwellings of men, and on to perhaps their ultimate control by explosives and science.