The thundering engines of the Central Pacific are stalled in the quest to conquer the mighty Sierras. Only a mountain of a man, Darby Buckingham, could pound the railroad through the granite walls of trouble. Atop sheer rock cliffs just a death plunge away from the surging river a thousand feet below, braving punishing cold, Darby must lay down track, foot by hard-blasted foot, with a construction crew that is threatening to tear itself apart with vicious fighting. But as they climb toward the notorious Donner Pass they face the most brutal challenge - an avalanche of sabotage and murder...