While surveying a telegraph line in 1861, Western Union engineer Edward Creighton (Dean Jagger) is severely injured in an accident. He is discovered by Vance Shaw (Randolph Scott), an outlaw on the run from a posse. Forced to travel on foot after his horse was hurt, Shaw at first considers stealing Creighton's horse, but changes his mind and takes the man with him, saving his life.Sometime later, following his recovery, Creighton returns to Omaha, Nebraska and plans the construction of a telegraph line from Omaha to Salt Lake City, Utah. Facing considerable opposition to the line from Confederate soldiers, Indians, and outlaws, Creighton elicits the help of his sister Sue (Virginia Gilmore), foreman Pat Grogan (Minor Watson), and assistant Homer Kettle (Chill Wills).Looking to put his outlaw past behind him, Shaw arrives at Creighton's Western Union office looking for honest work and is hired as a scout by Grogan who is unaware of his past. Creighton recognizes him among the men and al