Hoppy, Johnny and Windy are fighting a malicious gang trying to stop a cattle drive from reaching a drought-stricken North.
Belle Starr has returned from time in prison only to face a hail of bullets, along with rescue by Hoppy and the Bar 20 gang.
An evil deputy is using Indian half-breeds to rustle cattle. This causes trouble between the cattlemen and Indians. Hoppy, Windy and Lucky see that justice is served. Songs abound.
Hoppy clears Lucky on a charge of bank robbery and foils the plot of a crooked lawyer to rustle a herd of pedigree cattle and take over the valley.
Lorna Drake has inherited a ranch. Hoppy teaches her a bit about ranching and handles Scar Lewis, the bad guy, in the process.
Hoppy's brother has been murdered and he is on the trail of the murderers. To get them he makes himself seem to be a wanted man.
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 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.
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."
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 and Lucky are headed to South America to deliver a heard of cattle. Bay guy Ralph Merritt gets in their way. For a while.
Escaped criminal "The Fox" hates Hoppy and a Rurales colonel for imprisoning him and lures Cassidy to Mexico in order to exact his vengeance.
When the outlaw El Toro saves Hoppy's life, Hoppy agrees to find his missing grandson.
Burton is after Clark's ranch. He gets the banker to refuse to renew Clark's note and then sends his men to rustle his cattle. Hoppy is Clark's new foreman and is on to Burton's scheme. But just as he learns of the rustling and is about to go after the gang, the Sheriff arrives and arrests him for hiding Johnny who has been accused of robbery.
Hoppy, Lucky and California are chasing cattle rustlers who have been bothering cattle rancher friends of Hoppy. A crooked foreman is the source of the trouble. Johnny and Lucy are the love focus.
A bad guy has used several murders to drive all the inhabitants out of town in order to give his gang access to the oil which lies under the land.
Hoppy, California, and Lucky travel to Mesa City for a short vacation. California buys new clothes and carrying his old ones in a suitcase, bumps into escaping bank robbers in the dark. His suitcase gets switched with that of the robbers and he is seen with the money. Hoppy must find the money that has mysteriously disappeared and also the robbers so that he can clear California who is now in jail.
One of Hoppy's Bar 20 ranch hands is tricked into participating in nefarious activities after being subjected to hypnosis.
The Bar 20 boys are after Nevada and his gang of cattle rustlers. Hoppy and California join Nevada's gang under assumed names. Johnny and the rest of Bar 20 get directions from Winters and head out looking for Hoppy's signal. But Winters wanders on ahead and gets spotted. This lets Nevada trap them in a canyon and to make matters worse, Hoppy's masquerade has been exposed.
Belle Langtry runs a town being taken over by cattle rustlers. She is also a front for the outlaws, who are led by Steve Fraser. Hoppy gets elected sheriff and cleans up the town with help from the Bar 20 boys.