Riders of the Timberline (1941)

Cuando un amigo de Hoppy muere al intentar huir de la cárcel, le echan la culpa a él y le expulsan de los Texas Rangers.

La llegada de la ingenua maestra June Lake al villorrio donde el caballeroso Hopalong Cassidy tiene su famoso rancho Bar 20, revoluciona la vida de los vaqueros. Pero también irrumpe por allí el cuatrero Sutton, quien con sus forajidos aterroriza a los pueblerinos y roba el ganado del rancho

Cuando deciden comprar la mitad de un rancho, Hopalong Cassidy (William Boyd) y sus compañeros, California y Johnny, se verán en líos cuando alguien quiere monopolizar el agua y además presiente que, en aquella tierra, hay petróleo de por medio.

La diligencia en la que viaja Marie Stevens con su madre y su padrino de boda, es asaltada, y a Marie le roban las joyas que le diera su prometido Richard Adams. Hopalong Cassidy y su par de colaboradores les rescatan de los bandidos, pero ciertos hechos harán que se conviertan en sospechosos de estar aliados con quien cometieron este robo.

Posing as a cattle buyer, Hoppy crosses over into Oklahoma where the Jordan brother's and their outlaw gang operate outside the law. After receiving an unfriendly reception when he finds them, he, California, and Johnny rustle their cattle and drive across the river into Texas. He hopes they will cross over to retrieve their cattle and then he can arrest them.

Finishing a trail drive, Hoppy and the boys head to town and immediately get caught up in the conflict between school teacher Miss Abott and next door saloon owner Mawson. When Miss Abott disappears, Hoppy gets a clue to her location and rescues her from Mawson's cabin. It looks like Mawson is the man he wants, but Hoppy finds an item that indicates otherwise.

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.

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.

At the reading of his late cousin's will, California learns the estate will be divied among whoever remains of the seven relatives. With one already dead, another immediately murdered, and the Lawyer telling them the ranch is almost worthless, Hoppy investigates.

Dos 'rangers' de Texas acuden en ayuda de un colega ahora establecido en California. De esta manera matarán dos pájaros de un tiro, ya que persiguen a un forajido que huye hacia California. Allí se encontrarán con una banda de malhechores que roban grandes propiedades.

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.

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'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.

Hoppy's ranch is threatened by rustlers. Hoppy and the gang oblige as usual.

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, Johnny and Windy are fighting a malicious gang trying to stop a cattle drive from reaching a drought-stricken North.

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.

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."

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.