After seeing a number of Rex Allen films recently I've come to the conclusion that Herbert J. Yates was trying to create a new Roy Rogers and Dale Evans by teaming Rex in so many films with Mary Ellen Kay as a singing partner. In Border Saddlemates they even recycle one of Roy's best songs Roll On Texas Moon into Roll On Border Moon. Sad to say that the day of the B western programmer was coming to a close and Yates at Republic did not have a clue.
This is obviously a Roy Rogers plot here. Rex Allen is a veterinarian in this film who is starting a new practice and he retains Slim Pickens as his assistant as a most unsuccessful dog catcher. Dr. Allen gets himself involved with Mary Ellen Kay, her younger brother Jimmy Moss and their uncle Forrest Taylor. They run a fox farm, they raise foxes that are trapped in Canada and shipped to Montana. Roy Barcroft who runs a trading post north of the border traps the foxes who eventually will wind up as fur stoles.
The veterinarian before Allen was a dupe however, his function was to inspect the foxes for disease as they go across the Canadian border. But Barcroft is shipping counterfeit money in false bottoms of the cages. And Taylor sells the foxes to certain buyers in the states who distribute the the bogus money. He's in the racket because Barcroft knows about his criminal background that the kids don't know.
When young Moss's pet fox gets sick, Allen wants to examine and treat him and places a quarantine on the foxes being shipped. That throws a monkey wrench into the plans of the villains and Barcroft orders the pet to be kidnapped killed and the body hidden so Allen can't do an autopsy and prove there was disease in the fox population. That fox-napping sets off all the chain of events that bring the villains down.
I have to say this one was original in plot if nothing else. And the fox-napping leads to a hilarious scene with Slim Pickens. Barcroft's henchmen order him to take his boots and pants off and they throw them into the furnace to prevent him from following. But that deters Slim not a wit as he straps his gun over his long johns and follows picking up a fully clothed Allen all the way. As a funny sidekick Slim was at his best in Border Saddlemates.
In fact this is one of Allen's best films for his time at Republic Pictures.