Hoppy is busy chasing stagecoach bandits who sing as they rob.
Lee Garvin has eloped with the daughter of a railroad man who didn't approve of the marriage. Hoppy steps in when the young man is framed for murder.
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.
Hopalong Cassidy and Johnny Nelson ride to the mountains to help a man and his daughter save their logging business from someone who is sabotaging their efforts.
When Ranger Hoppy's falsely accused young ranger friend is killed while supposedly trying to escape from jail, Hoppy is blamed and drummed out of the Texas Rangers.
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.
Hoppy and new sidekick California Carlson head to California to help out Lucky Jenkins.
Hoppy, California and Lucky arrive at a remote inn, where Lucky expects to be married - but finds the bride-to-be in distress over her uncle, who has suddenly disappeared from the inn. Then Hoppy finds the uncle's body in the shaft of his nearby mine...
Hoppy, California and Johnny partner up with brother and sister ranch owners, two of several who are having their access to water blocked by a dam owned by a greedy merchant in town, who is intent on driving them out and taking their land for himself.
Hoppy, California and Lucky take refuge from a storm inside a supposedly abandoned church outside a ghost town, only to meet a young woman and her mother there, then find themselves surrounded by a gang of "workmen" intent on tearing down the church if they have to kill the five to do it.
Hoppy and his pals arrive in a remote town to investigate the counterfeiting of both U.S. and Mexican money; his only clues are the name "Mordigan" and a drawing of a comet. He quickly finds out that Mordigan is the town "boss"; but what or who is "the comet", and why are Mordigan and his henchmen intent on persecuting a young woman, her drunken brother, and her deathly ill sister-in-law who've also just arrived in town?
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.
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.
Stagecoach robbers take the money Hoppy was going to use to buy cattle so Hoppy, California and Lin go after them.
When the outlaw El Toro saves Hoppy's life, Hoppy agrees to find his missing grandson.
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.
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.
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.
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.
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.