Based on "Sister of the Road," the fictionalized autobiography of radical and transient Bertha Thompson as written by physician Dr. Ben L. Reitman, 'Boxcar' Bertha Thompson, a woman labor organizer in Arkansas during the violence-filled Depression of the early '30's meets up with rabble-rousing union man 'Big' Bill Shelly and they team up to fight the corrupt railroad establishment and she is eventually sucked into a life of crime with him.