A series of reversals bring two desperate people together. When a saloon owner is framed by his partner for a stagecoach robbery, he fights to secure an acquittal.
When his cattlemen abandon him for the gold fields, rancher Wil Andersen is forced to take on a collection of young boys as his cowboys in order to get his herd to market in time to avoid financial disaster. The boys learn to do a man's job under Andersen's tutelage, however, neither he nor the boys know that a gang of cattle thieves is stalking them.
A posse discovers a trio of men they suspect of murder and cow theft and are split between handing them over to the law or lynching them on the spot.
Bob Tyler has rustler trouble while driving a herd of cattle to the new owner, but he refuses to turn the herd over to Frank Kellogg. He has a run-in with Jean Polk, discovers she is the owner of the cattle, and is fired. With his friend, Barney McCool , Bob snoops around and discovers that Kellogg is behind the rustling.
A peace-loving man named Ben Kane takes a job as deputy marshal of Lords, in the old West. Kane is no lawman, but he accepts the badge because he has an old score to settle with the town's chief trouble-maker. Once on the job, Kane must also deal with a young sharpshooter named Billy Young and a sharp and sassy saloon dancer, Lily.
A band of murderous cowboys has imposed a reign of terror on the town of Warlock. With the sheriff humiliatingly run out of town, the residents hire the services of Clay Blaisedell as de facto town marshal. He arrives along with his friend, Tom Morgan, and sets about restoring law and order on his own terms whilst also overseeing the establishment of a gambling house and saloon.
Notorious shootist and womanizer Quirt Evans' horse collapses as he passes a Quaker family's home. Quirt has been wounded, and the kindly family takes him in to nurse him back to health against the advice of others. The handsome Evans quickly attracts the affections of their beautiful daughter, Penelope. He develops an affection for the family and their faith, but his troubled past follows him.
After escaping from jail, outlaw Wes McQueen is convinced by his old partner in crime to do one last heist.
When Matt Kilgore and his men frame and then hang an innocent man, Lige Saunders sends for his son Wild Bill Saunders who arrives to find his father shot by Matt's brother. When the brother is killed in his fight with Bill, Matt sends two fake Deputies to arrest Bill whom he then plans to hang. But Matt's sister, attracted to Bill, overhears the plan and rides for help.
Jim Lockhart is out to capture the robbing and murdering "Solitaire Kid".
The local school is causing Hoppy problems. First Bar 20 cattle are stolen when Hoppy investigates a problem there. Then the new teacher arrives and disrupts the routine of the Bar 20 hands. Later with the Bar 20 hands at graduation, the rustlers are poised to strike again. But there is dissension among them and this will lead to the break that Hoppy needs.
Escaped criminal "The Fox" hates Hoppy and a Rurales colonel for imprisoning him and lures Cassidy to Mexico in order to exact his vengeance.
Caldwell and Nixon have their men rob the stage and then critcize the Sheriff for not catching the robbers. With her father the Sheriff under pressure, Mary sends for Hoppy who finds the stolen money and sets a trap to bring in the entire gang.
Hoppy and Lucky are headed to South America to deliver a heard of cattle. Bay guy Ralph Merritt gets in their way. For a while.
Buck Colins heads a group of local ranchers who are trying to prevent the railroad from completing its line through their property. Till now they have been able to charge tolls on herds passing through. Hoppy goes undercover to expose them.
Hoppy goes to town to help Marshal Windy with some rustlers and winds up helping the widow Joyce when confidence men try to take her herd. King's Men songs include: "Hi Thar Stranger" and "Lazy Rolls the Rio Grande."
Hoppy goes undercover as a gambler from the East when Bar 20 cattle are stolen by unknown rustlers. Brennan/Talbot are twin brothers (one a casino owner, the other a rancher) and Hoppy believes they provide alibis for each other while one is out committing crimes. Hoppy gets a job in the casino to learn more but is exposed when a gambling gunslinger notices him.
U.S. Marshal Hopalong Cassidy is called when a town becomes overun with bad guys. Disguised as a member of a medicine show, Hoppy discovers that the ringleader is none other than sweet li'l ol' Ma Burton.
A crusading newspaper editor recruits his old friend Hoppy to take the job of Marshall in a town rife with vice and murder directed at helpless miners.
On a cattle drive Hoppy, camp cook Windy, companion Lucky, and young Artie Peters encounter an eccentric professor. The professor professes to be searching for the evolutionary missing link, but in reality he is a cattle rustler who uses his dynamite to scatter the cattle in order capture some of them. Hoppy and Bar 20 guys ultimately capture the professor.