Alaskan railroad magnate Curtis Gordon hires engineer Dan Appleton to design a railroad route up the Salmon River to the rich gold country Gordon turns down the engineers proposed route in favor of his own and Appleton quits Murray ONeil a rival builder hires him and falls in love with his sister Eliza while Appleton courts Natalie Gordons stepdaughter Following Appletons plan ONeil lays the trail with a bridge crossing the river in face of Gordons opposition