Joan sends Jim into the untamed mining camps of Idaho Territory to prove his grit and spirit. Immediately regretting their quarrel, she sets off to bring him back. However, a stagecoach bandit captures her and intends to keep her as his woman.
During the building of the Union Pacific Railroad across the plains to meet up with the Southern Pacific in Utah, Warren Neale, civil engineer, contends with natural obstacles and meets Allie Lee, the sole survivor of an Indian raid in the Black Hills.