Mysterious deaths have been occurring in the same towns as Miller's Circus and the Governor has sent Ken Kenton to investigate. Ken joins the show but when he realizes that Bargoff is involved, Bargoff has fled and taken Mary Hiller as a hostage. The trail leads to Baron Petroff who concocted the deadly chemical and Ken quickly finds himself the Baron's prisoner.
Captain Porter's scheme is to buy livestock and then have his men show up later to kill the buyer and retrieve the money. When his men kill the next victim, he frames the Arizonian for the murder. The Arizonian escapes the law and joins up with the outlaw Vasquez. Knowing Porter's scheme, he plans to trap him by using Vasquez as the next buyer.
Jim Brandon, foreman of the Wind River Ranch, owned by Martin Stavnow, is in love with Ronnie, the rancher's daughter, though he is unaware that Harvey, a youthful cowhand, also loves her. Thus, Jim asks the boy, whom he protects like a brother, to speak for him. When he is spurned by Ronnie, Harvey decides to join Red Slade's gang, who are plotting a raid on the Wind River herd. As Jim forcibly attempts to separate him from the gang, Harvey is killed; and through the aid of his horse, Tarzan, Jim foils Slade's attempt to stampede the herd. Slade takes refuge in a wagon where Ronnie is hiding; Jim rescues Ronnie from the wagon just before the runaway team plunges over a cliff with Slade riding to his doom.
After El Lobo robs Don Jose he gives one of the stolen items to Conchita. Later when he saves Anita in a runaway coach, Don Pedro invites him to the wedding of Anita and his son Don Jose. But Conchita is at the wedding and recognizes him putting his life in danger.
After being shot, a dying Marshal Dawson gives Dave Hayes his badge and asks him to finish his job. Dave becomes Marshal but when Bowie, the man that shot Dawson appears, he exposes Dave as an imposter. Dave is then in trouble when Edwards incites the mob to lynch him.
Colonel Lee, a homesteader, is the object of terrorists who want to drive him off the range so that his horses cannot be entered in the county races, and he refuses an offer of Martin Brierson to buy him out. Pete, Brierson's brother, in hiding because of his criminal record, burns the colonel's barn and injures his horses. Convinced of Brierson's responsibility for the terror tactics, "Lucky" Larkin plans to ride Tarzan, the colonel's pet colt. Brierson does his best to disqualify the horse, but Larkin tricks him and wins the race. Larkin captures Pete and forces him to confess. The Brierson brothers are brought to justice, and Larkin wins Emmy Lou, a homesteader's daughter.
Bud Rand, a cowboy who is charged with the care of Little Billy Rand, accepts an offer to appear with Copeland's Wild West Show to ride a horse called "Mankiller." Dude, Copeland's righthand man, resents Bud's attentions to Mary, one of the performers, and when they fight it out, Bud is the victor. In revenge Dude loosens the cinch on the horse.....
Bill Hollister (Jack Hanlon) organizes a wagon train to break the unfair monopoly held by Jake Lynch (Tom Santschi) on food prices in the mining camps. The Rambler (Ken Maynard) joins the train when it leaves for Gold Hill, and takes command when Hollister is killed from ambush. Jacques Frazelle (Al Ferguson) schemes to get rid of The Rambler and win Sue Smith (Edith Roberts). He plots with Lynch to disrupt the train, but The Rambler beats him in a whip-fight...
Dick Scott takes his Wild West show to the Balkan kingdom of Alvania where the boy king of the country commands the troupe to give a performance. The king is greatly impressed with the American cowboys and makes them his palace guard. The prime minister starts a revolution, and Dick and the Americans put it down. The boy king sanctions a romance between Scott and Ruth Elliott, the royal governess.
Cal Roberts can ride anything with four legs. He enters the contests held at big rodeo. He wins all honors and meets a girl who races horses to help her father clear pressing debts. Complications follow, but Cal wins the girl.
After a work crew stringing telegraph wires across the Great Plains is slaughtered by Indians, Pat O'Leary, the company superintendent, must take out another supply train to make the dangerous trip across open country. The Indians attack and are driven off. On the day the wires are finally strung, the settlers gather to hear the first message from the East.
Assigned to catch a gang of outlaws, officers Bruce Kenton and Paddy Halloran rescue Helen Morgan when her wagon is attacked by the very same gang. Through a ruse, Kenton manages to infiltrate the gang, which is holed up in the lawless community of Caribou Flats. While in the employ of villainous trading post operator Jack Blake, Kenton discovers that Blake is not only the leader of the gang but also the man who murdered Helen's brother.
The honest John Graham and the crooked Ross Cheswick battle for supremacy. Despite Cheswick's unscrupulous methods, Dan and his handsome bronco Tarzan win the Big Race for Graham. Dan's prize: Graham's lovely daughter Sally.
Steven Bancroft, a young officer in the U. S. Calvary, is given the assignment of ensuring that dirty-work by agents of Spain, Mexico or Russian aren't going to keep statehood-for-California from becoming a reality. Bancroft uses his guns to settle any debates regarding international laws.
Colonel Beldan runs a Wild West show. When Beldan's star attraction switches to his unscrupulous competitor Vicarino, the young Bob Mason takes the opportunity to take over the job with his horse 'Tarzan'.
From Death Valley in the Mojave Desert to Mount Whittier, the outlaw gangs are wreaking havoc on the gold and money shipments from the mines and ranches. Wells Fargo organizes an express service that will insure the shipments and ensure a guaranteed delivery. Granger Hume is hired to help Wells-Fargo deliver on their promise.
Deputy Marshal Jerry Steele (Ken Maynard) heads off to Oklahoma where a gang of nasty cattle rustlers is terrorizing the local ranchers. After a bit of detective work -- greatly aided by a motley group of would-be outlaws deputized for the occasion -- Steele unmasks a supposedly upstanding citizen Bob Crew (Tom Santschi) as the leader of the rustlers.