Cowboy Jeff Larabee returns from the east and meets Doris Halloway, a young girl, that he regards as a vagabond, till he learns that she's the owner of the farm where he works. He tries to win her heart, but without success, until she is endangered by gangsters
Hoppy, Johnny and Windy are fighting a malicious gang trying to stop a cattle drive from reaching a drought-stricken North.
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.
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.
Cattle rustler Nevada dreams of living like an emperor in the West. Hoppy and the Bar 20 boys aim to put an end to his dream.
Hoppy goes undercover as an outlaw (which permits him, for once, to drink and be mean to children) to track down a bunch of outlaws operating along the border. Loco, the head bad guy, deflects suspicion from himself by pretending to be a moron.
Problems come in the form of one of Hopalong Cassidy's neighbors, but the matter is settled when Hoppy roots out the troublemaker.
Lorna Drake has inherited a ranch. Hoppy teaches her a bit about ranching and handles Scar Lewis, the bad guy, in the process.
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.
An evil gang is involved in both cattle rustling and the robbing of stagecoaches. Hoppy must stop them without help from the sheriff who turns out be a major outlaw himself.
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.
Disguising himself as a milquetoast Easterner who writes Western novels, Hoppy enrolls in a dude ranch in order to unmask the murderer of the owner's husband.
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.
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.
Escaped criminal "The Fox" hates Hoppy and a Rurales colonel for imprisoning him and lures Cassidy to Mexico in order to exact his vengeance.
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.
Julie's husband has been murdered and land agents want her to sign away her property rights. Hoppy warns against this but she does so anyway. It looks as though she will be unable to deliver the timber called for in her agreement. Hoppy has to make the lumber deal happened and solve the murder.
Hoppy, Johnny and California go to Arabia to buy some horses. There they get involved with a sheik and a harem and a kidnapping plot.
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.