 After finding a vital pass through the Canadian Rockies for the building of the Canadian Pacific Railway, Tom Andrews (Randolph Scott) tells his boss Cornelius Van Horne (Robert Barrat) that he is resigning to marry the girl he loves, Cecille Gautier (Nancy Olson.) From Cecille, Tom learns that fur trader Dirk Rourke (Victor Jory) fears the coming of the railroad because it threatens his hold on the Indians and other trappers. Tom and Rorke have a bitter fight over Cecille, and Tom asks her to wait for him, as he has to go back and finish his job with the railroad. Aided by Dynamite Dawson (J. Carroll Naish), Tom finds evidence of Rourke s work against the railroad construction and almost loses his life when Rourke fires into some crates of dynamite Tom is unloading. The construction camp s doctor, Edith Cabot (Jane Wyatt), gives her own blood in a transfusion to save Tom s life. Cecille, realizing that her father (John Parrish) is working with Rourke against the railroad,rides off to warn Tom. Rourke intercepts her and tells her that Tom is in love with the lady doctor, but she bullwhips him and gallops off.