In the 1860s, Mary Marlowe defies her father's wishes to marry a British lord and runs away with clerk John Carlton as he heads West to make his fortune. Mary and John endure the difficult journey and settle into a small cabin, then face the hostilities of a cattle rustling gang, as well as the tragic loss of their only son. With Mary's help, John defeats the gang, which propels him to political power that, over the years, gradually erodes the once-happy marriage.