During a cattle drive, Don McGow leaves the herd in charge of his younger brother and rides off. When the herd is reported stolen he blames himself and goes in search of the thieves.
Capt. James Stewart pursues the bandit "The Kinkajou" over the Mexican border and falls in love with Rita, though he suspects that her brother is the bandit.
To get the Delaney ranch Cole's henchman Anders has started a phony range war between the cattlemen and sheepmen. After killing Delaney, he tries to kill his daughter Jill and then Roy who was sent to investigate the war. But the failed attempts gives Roy the information he needs.
The setting is a small town in 1870s Pennsylvania. Sally Waterson and her father have stopped in town with their traveling medicine show, but when their wagon catches fire, they find themselves stranded. They're taken in by Mrs. Cortlandt and her grandson, Peter, who is trying to set up a pipeline that will supply oil throughout the state. Sally and Peter soon fall in love and marry. Neither their marriage nor Peter's pipe dreams flow too smoothly.
Hoppy returns to find Johnny in trouble. Buck Peters has been shot by Porter who made it look like Johnny did it. When Johnny flees he runs into Linda. He takes a liking to her only to learn her father Shanghai is one of Porter's gang. Going after Shanghai, he gets captured by the gang and Porter now plans to kill him. But Hoppy is near by and Johnny will get unexpected help from Shanghai.
The U.S. Army needs more horses for the Spanish-American War. Hoppy must turn his Bar 20 cowhands into Rough Riders to gather up the horses, and of course bad guys try to sabotage the operation.
An evil ranch foreman tries to provoke a range war by playing two cattlemen against each other while helping a gang to rustle the cattle. Each cattleman blames the other for missing cattle. With the help of Bill Cassidy (Hop-along, because of an earlier bullet wound) and Johnny Nelson, the warring cattlemen join forces to do in the outlaws.
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.
Hoppy's friend Dennis owns a rich gold mine. Frazier who owns the adjoining mine and wants the Dennis mine, has Dennis killed. Hoppy steps in to take over running the Dennis mine and learns Frazier's men sneak into and work the Dennis mine at night. Hoppy captures one of Frazier's men only to be captured in return by Frazier and left to die in a burning building.
Posing as a cattle buyer, Hoppy crosses over into Oklahoma where the Jordan brother's and their outlaw gang operate outside the law. After receiving an unfriendly reception when he finds them, he, California, and Johnny rustle their cattle and drive across the river into Texas. He hopes they will cross over to retrieve their cattle and then he can arrest them.
European bad guy Baron Bendor leads some local townsmen in a plot to obtain horses through theft. Hoppy and his sidekicks Lucky and Speedy must find and expose the horse thieves.
As rustled cattle have mysteriously disappeared, Johnny sends for his friend Hoppy, Hoppy arrives and immediately suspects Dan Slack. Realizing his telegram about Slack was intercepted, he locks up the operator Lafe knowing he can escape. Tailing Lafe he finds a secret entrance to a mine and inside finds the missing cattle. But Slack's men also find him just as the cattle are stampeded through the mine shaft.
Hoppy and Lucky have been called in to investigate a series of stage holdups. The robbers are taking gold from Colby's mine and Hoppy suspects it may be ex-outlaw Colby himself. When Speedy strikes gold, Hoppy borrows it and announces a gold shipment hoping to catch the gang and their leader.
When three Texas Rangers try to investigate kidnapped Mexicans being used as forced labor in the mines of Silver Bullet, they are framed for murder by the town's corrupt sheriff.
Brady Hawkes has to run to his son's rescue once again in this continuation of the Gambler stories. Jeremiah is now a young man who has become involved with Butch Cassidy and the Sundance Kid. Brady pursues the gang in order to get Jeremiah out of the gang before he gets in too much trouble with the law.