John Blaine wins a contract to build a section of the Transcontinental Railroad. With his daughter Ann and his eighteen-year-old son, Noah, Blaine establishes his construction camp in the heart of Wyoming, on the border of hostile Indian territory. Forces led by Rance Judd, Bart Eaton, and the renegade Buckskin Joe, unite to stop Blaine from completing the job on time. But with the leadership of construction engineer Tom Crosby and young Noah, the hardships of railroad pioneering are overcome.