Ten years after the Civil War has ended, the Governor of Texas asks Leander McNelly to form a company of Rangers to help uphold the law along the Mexican border. With a few veterans of the war, most of the recruits are young men who have little or no experience with guns or policing crime.
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.
Texas Ranger Jake Cutter arrests gambler Paul Regret, but soon finds himself teamed with his prisoner in an undercover effort to defeat a band of renegade arms merchants and thieves known as Comancheros.
Texas Ranger Buck Dunne is assigned to round up a gang of bank robbers. The leader of the gang turns out to be the "respectable" Judge Longstreth, making life difficult for Dunne inasmuch as he's in love with Longstreth's niece Barbara.
The Texas Rangers round up rustlers by masquerading as the same. Trouble ensues when while in disguise one of the Rangers is accused of a killing.
Someone has been stealing ore from a valuable smelting mine. One of the independent mine-owners victimized by the crooks is pretty Joan Manning, making the Rangers' mission a bit more pleasant.
In this western, fake settlers make themselves at home on an ex-ranger's ranch and drive him away. A shady newspaper publisher and a gambler then conspire to take over the land. Fortunately, another ranger endeavors to help his pal. Enlisting the aide of his fellow rangers, they get oust the homesteaders. The publisher and the gambler shoot each other and the retired ranger gets his ranch back.
Cal Stanley goes undercover as a beef buyer in order to catch the gang responsible for stealing the area's cattle.
To prevent a lynching, Ranger Tim lets two outlaws go saying he will get them later. This gets him kicked out of the Rangers and he goes across the border and joins Big George's gang who are running contraband. But the outlaw Jimmy overhears Tim tell his sister that the dismissal was a fake. Big George and his gang then go after Tim and trap him in a cabin.
With thousands of cattle being rustled from White Sage ranch the 1930's Texas Rangers are called in. They manage to get one of their agents into the gang by making them think he is the Pecos Kid on the lam.
An undercover Texas Ranger runs into trouble when he learns that the murderer he's trailing has a twin brother.