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.
Lorna Drake has inherited a ranch. Hoppy teaches her a bit about ranching and handles Scar Lewis, the bad guy, in the process.
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.
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.
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.
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.
Escaped criminal "The Fox" hates Hoppy and a Rurales colonel for imprisoning him and lures Cassidy to Mexico in order to exact his vengeance.
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.
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.
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, 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.
Hoppy is an agent of the federal government investigating the counterfeiting of both U.S. and Mexican money. His only clues are the name "Mordigan" and a drawing of a comet.
A town bedeviled with outlaws sends for Hoppy, Lucky and California after their own vigilante committee fails to solve the towns problems. Hoppy discovers that the bad guys are led by the town boss, and so are the vigilantes.
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.
A gang of outlaws are using force to become possessors of every ranch in the area. Hoppie, of course, is out to stop them.
Hoppy's ranch is threatened by rustlers. Hoppy and the gang oblige as usual.