Heading up the Chisholm Trail with a small herd and just a few men, Breezy has his cattle rustled by Curley and his gang. Returning to Texas, Breezy convinces the ranchers to send their cattle north in one big herd guarded by a lot of men. Outnumbered, Curley has a plan to get the cattle.
Brad Buckner has just bought a ranch. Murdock keeps his rustled cattle on the ranch and sends his men to kill Buckner just as they did the previous owners. But Buckner and his men foil their attempts and decide to search the ranch. To throw Buckner off he kidnaps Buckner's girlfriend and the Sheriff and makes plans to drive the cattle across the border.
Rancher William Norton refuses to sell his cattle for half price, so saloon owner and gang leader Jim Fletcher, contrary to the orders from his secret boss Willard McGowan, the town banker, has his men rob and beat up Norton. Unknown to anyone, Marion, McGowan's adopted daughter is really the daughter of Norton, who disappeared as a young baby when she and her mother were passengers on a stagecoach held up by McGowan. Chuck Saunders, Norton's foreman, goes after the gang for robbing his boss and eventually uncovers the truth regarding Marion's heritage.
It's 1861 and Buck gets the business men of Sacramento to establish the Pony express. Hawley runs the stage line over the same route and has the U. S. mail contract. When it looks like the Pony Express will be awarded the mail contract, he gives guns to the Indians and has them attack both the riders and the stations.
Ted Haley rides to his brother's ranch and finds him dying from a knife wound. The brother names Sol Rothert as his killer. Leaving the house, Ted doesn't notice a mysterious man watching him, but he sees a rider gallop up to the house and enter, and Ted rushes to investigate.
The gold mine belonging to "Gun" Barlow is worked out, and Barlow attempts to buy adjacent land, with the hopes his gold vein will continue, from town postmistress Marion Saunders who, keeping a vow she made to her father on his death-bed, refuses.
Sayres and his outlaw gang operate out of a town just across the border and out of the jurisdiction of the Texas Rangers. Ranger Bob Allen is sent across the border where he poses as an outlaw hoping to lure the gang back into Texas. He gets into Sayres' gang displacing the gang boss but the disgruntled ex-boss is able to expose the hoax and Bob is made a prisoner.
Bob Allen in his starring debut gets a job on Wright's ranch where he hopes to find the rustlers no one else has been able to locate. Everyone is looking for men when the actual rustler is a horse.
The McLean and Brennan ranches are both losing cattle to rustlers and each blames the other when cattle buyer Graves is the real culprit. To throw suspicion off himself Graves hires Tim to investigate, not knowing that this will be his downfall.
Newcomer Torrent wins $500 from Olcott and $500 and a wild horse, by riding the horse, from Engle. Then loses the $1000 to Engle in a poker game. Torrent goes to work for Olcott. Torrent fights with Stark and Stark quits and goes to work for Engle. Rustlers are stealing horses. Carson suspects Olcott and Olcott suspects Carson. Sheriff prevents war between them. Torrent stops wild horse stampede. Starks spills beans on Engle. Torrent kills Engle and wins Patsy Olcott.
On parole from prison for a murder he did not commit, and not allowed to carry a gun, Buck sets out to find the real killer. His clue is a corner torn off a wanted poster with some handwriting on it.