A bandit known as the Fox is leading his band of outlaws burning ranches, rustling cattle, and committing all other sorts of crimes on both the US and Mexican border. Colonel Gonzales, of the Mexican Secret Service, and Major Stafford of the Texas Rangers devise a plan to have Ranger Johnny Nelson arrest Hoppy and have him (unknown to everyone except Col. Gonzalez, Maj. Stafford, and Hoppy) go undercover as an outlaw, be discredited and join the Fox's gang, despite having to go against his character by yelling at everyone from Johnny, Windy, boarding house owner Grace Rand, and her handicapped daughter Molly. Unknown to Hoppy, the Fox is really Loco, the village idiot who is able to find out all sorts of information and pass it on to henchmen Parker and Morgan (who introduces himself as the contact between him and the Fox.) The Fox later suspects that Hoppy is playing a trick with his bad guy persona, and kidnaps Windy and Molly taking them to his shack in the desert. Hoppy follows along, but can he overcome the Fox having his two friends hostage and Morgan and other henchmen racing in the cabin for a shootout. A very different and excellent entry in the series with great performances by the entire cast. Boyd is able to brilliantly go against the Hoppy character that we all are familiar with. Ankrum is able to be sinister (which he always did well) throughout playing both the Fox and Loco. Stunningly photographed and the direction by Watt creates lots of suspense and action, even though at 82 minutes (the longest Hoppy film) there are several slow stops, but is countered by the tense filled climax (perhaps the best of any Hoppy film). Rating, based on B westerns, 9.