Ken Maynard's exceptionally intelligent horse, Tarzan the Wonder Horse, is the star of this western about evil cowboy Steve Frazer (Welch) who gathers horses for slaughter, whose meat is sold to pet food manufacturers. The wild horse Tarzan frees the doomed horses from their corrals, and Frazer convinces the Sheriff that Tarzan is a threat and can be shot on sight. Local cowboy Ken Benson (Maynard) and rancher Pat Riley (Kennedy) work together to clear Tarzan's good name and put Frazier behind bars for his evil deeds.
When the Sioux come to Canada, the Canadians permit them to stay in Canada if they come peacefully. However, some cowboys kill all inhabitants of one of their villages. The cowboys seek to get back their horses, but they pretend to search for a girl who once had been robbed by the Indians.
Bill Carson arrives and tells Cash Horton that his supposedly worthless mine contains valuable tungsten. Duke learns of the mine's value and tries to have them both killed. Failing, he has the Sheriff arrest Bill for murder. Unknown to Bill and the Sheriff, the victim is alive and well.
Trouble starts when Bill Larkins and his two sons move in with his brother Joe. They start rustling cattle and then kill Rod's father with Joe's gun. The Sheriff and Rod think they did it and are after proof.
Bob arrives looking for the killer of his uncle. When the Sheriff chases him and his partner Rusty, Reno thinks they are the men he is looking for and takes them into his gang. There Bob finds his uncle's gun and knows he has found the right gang. However he realizes the gang has an unknown leader and he sets out to find him.
A crusty old rancher hires three young women to pose as his daughters. However, the real father of one of the daughters finds out about it, and kidnaps her to hold her for ransom--which the rancher can't pay.
A notorious outlaw being escorted to prison by a homesteader and his wife turns out to have satanic powers. He uses them on the man's wife to try to possess her and help him escape.