Hoppy, Lucky and California search for a mine owned by Trudy Pendleton after it was taken from her by thw swindling gambler Ace Gibson. They find the mine and Hoppy fights Gibson over it.
Three bodies turn up in a frontier hotel. Hoppy solves the murders and chases the killers through unusually misty and dark locations.
Hoppy is leading a scientific expedition and the Chinese who have a hidden settlement nearby are trying to stop them. Saulters and his outlaw gang are also in the area looking for a gold mine. When Saulters men attack, the gold mine is found. Hoppy agrees to file for the Chinese and heads after Saulters in the chase to the land office.
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.
When the outlaw El Toro saves Hoppy's life, Hoppy agrees to find his missing grandson.
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.
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.
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.
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.
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.
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 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.
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.
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.
In this Roy Rogers entry, featuring a song written by Oklahoma Governor Roy J. Turner (making him and Lousiania's Jimmie Davis and Texas' W.E. "Pappy" O'Daniel possibly the only state governors to write songs used in a western), Flying U ranch owner Sam Talbot is killed by a fall from a horse. St. Louis reporter Connie Edwards comes to check a rumor that he might have been murdered. She goes to Roy Rogers, editor of the local newspaper, and he takes her to the reading of Talbot's will. The ranch is left to Talbot's 12-year-old ward, Duke Lowery, much to the dismay of Talbot's niece, Jan Holloway. After some attempts on Duke's life, Roy finally proves that Jan, Steve McClory and coroner Jim Judnick had Talbot killed and are conspiring to do the same for Duke, making Jan the last heir.
Kirby sends his henchmen to break killer Matt Brawley out of jail. But Brawley has already broken out and they return with Fuzzy instead. Realizing they think he's Brawley, Fuzzy plays the part. He and Bill plan to round up the gang but Fuzzy is in trouble when the real Brawley shows up to expose the hoax.
Sandwiched in between the numerous musical numbers, the Gabby Whittaker and Madden rodeo's are competing for bookings. When Gabby gets a date in Albuquerque, Madden has his man destroy his equipment. Roy finds a broken rawhide rope at the scene and uses it to bring Madden to justice.
Evil Grant Withers lets a killer horse loose to ruin valuable horses on nearby ranches. He hopes to shake down the ranchers for his "protection". Roy tracks down the bad guys, but is suddenly trapped by them. Peter Miles, a boy terrified of horses, overcomes his fear and rides for help to save the day.
A man tracks down the five outlaws who murdered his brother, all the while being shadowed by a mysterious Pinkerton detective.
Cholita, after a long absence in Mexico City, is returning home to take up her duties as head of the rancho and, as everyone expects, to marry her childhood sweetheart José. Expectations are somewhat dashed as she shows up with Fernando to whom she is engaged. This makes José and Cholita's uncle more than a little bit put out as Fernando is not only not a Mexican, he is also a city slicker afraid of the country.