Ted Haley rides to his brother's ranch and finds him dying from a knife wound. The brother names Sol Rothert as his killer. Leaving the house, Ted doesn't notice a mysterious man watching him, but he sees a rider gallop up to the house and enter, and Ted rushes to investigate.
Unable to legally capture and sell a herd of protected wild horses, corrupt rancher Rance Macgowan uses his trained killer horse, Volcano, to substitute for the real leader of the herd and cause havoc and death among the ranches. With the government about to drop the restrictions on rounding up the herd, the Three Mesquiteers find themselves in the middle of the controversy after their friend, Sheriff Miller is killed by Volcano.
The Louisiana Purchase is imminent and Gilmore is smuggling guns into St. Louis so his men can make him Governor of the new Louisiana Territory. But John Colfax fights to defeat Gilmore.
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.
The Transcontinental Broadcasting Company sends a sound truck and equipment to a ranch to obtain an audition from "Santa Fe" Evans and his musical cowboys (Oscar Gahan, Lloyd Perryman, Robert "Curley" Hoag, Rudy Sooter and Sherry Tansey.) Carver, arch enemy of Evans and a rival for the love of Carol Sheldon, fails in an attempt to spoil the audition. Carver frames Mr. Sheldon and Carol's brother Buddy on a charge, by Al Jensen, of receiving cattle stolen from him by Evans. Carver blames Evans for all of the Sheldon's troubles and, what with one thing or another, it looks like Evans and his cowhands will miss the big broadcast.
Brett runs a protection racket for an unknown boss. When Jeff Hayes arrives and opens a gambling den, they try to shut him down. Unlike the others who have given in, he plans to fight back.
Director Leslie Selander exhibits the sure-handed expertise that would endear him to latter-day western cultists in his 1937 formula western Sandflow. Buck Jones plays the son of a crooked land dealer. Seeking redemption, Jones rides through the west to compensate every rancher who was cheated by his dad.
A lawman poses as an outlaw, steals $10,000 from a cattle thief, then promises to return the money if he can join the gang--while finding a way to expose them.
Tex and sidekick Grass join McGill's traveling show. When Price has McGill's wagons burned, Tex becomes the county tax collector to earn money. This leads to trouble as one of those owing money is Price who says he will not pay. Business doesn´t go as plan.
The gold mine belonging to "Gun" Barlow is worked out, and Barlow attempts to buy adjacent land, with the hopes his gold vein will continue, from town postmistress Marion Saunders who, keeping a vow she made to her father on his death-bed, refuses.
Barbara Evans has $25,000 and Gifford is after it. When his henchman fail to get it he refuses to pay them. They then decide to double cross him and get the money for themselves. Gordon is trying to protect Barbara and he must not only take care of the two henchmen, but also Gifford and his phony Sheriff.
The Harper wagon train is carrying money and Bull and his gang are after it. When their first attack is foiled by the rangers, Allen trails them. But he is captured and his ranger badge used to divert the rangers away leaving the wagon train unprotected.