Chasing jewel thieves, Captain Carson and Magpie head for the border where Carson, posing as a Chinaman, opens a store that buys jewelry. To flush the thieves into the open, Carson wins all their money at poker. They agree to sell him the jewels but plan to kill him and keep both the jewels and the money.

Before he was killed, Martin hid a half million dollars worth of bonds on his ranch. Brainard, who killed him, Inspector Carson posing as Sam Brown, and Martin's niece Margaret all want the ranch, and it's being sold at auction.

A phantom-like gunman is murdering the hands at the Circle T Ranch and the Range Busters are recruited by its owner to stop the "phantom". Only, the ranch owner is killed before they can arrive. First film in the Range Buster series.

Bob rides into a border town where he runs into trouble with Lambert and his gang. Herb arrests him claiming he is the outlaw El Diablo. But it was just to save him from Lambert's gang and the two now plan to trap the outlaws.