Conductor Grant and engineer Jeff race their empty train east to collect a $3 million shipment of coal. And once the 152 cars are filled, they've got to get their mammoth convoy back over the mountains. Ahead of them in Glacier National Park, an avalanche warning forces snow removal crews to a halt. Railroad engineer Kent prepares for a high-altitude bridge inspection. And while the team races to replace a cracked junction, Jimmy's lack of discipline threatens to derail the operation. Meanwhile in Ontario, electrical issues on board the Polar Bear Express could leave Moosonee's minor hockey league out in the cold.

Winter may be over but spring presents a whole new set of dangers on the Rocky Mountain railroad. Lethal rockslides threaten Canadian Pacific's longest and heaviest train.