In the Rocky Mountains, surveyor Tom Andrews (Randolph Scott) tries desperately to find the best route for the Canadian Pacific Railway, with the help of demolitions expert Dynamite Dawson (J. Carrol Naish). A band of trappers opposing the new railroad tries to interfere by sabotaging the construction and inciting the local Native Americans to rebel against the project. Fortunately, Dr. Edith Cabot (Jane Wyatt) is on hand to bind the men's wounds and raise their spirits.