Thunderhoof (1948)

Texas rancher Scotty Mason goes into the Mexican desert-country in search of a wild horse, and takes his young wife, Margarita and his hired-hand, The Kid, whose life Scotty had saved a few years earlier. The Kid falls in love with Magarita before they have crossed the Texas border, and spends more time plotting to get rid of Scotty than he does horse-hunting. Before long the two are engaged in fisticuffs in a mountain pass, but Scotty spots the horse he is hunting (Thunderhoof) and the chase is on. Scotty breaks his leg in the capture and, with a make-shift splint, Scotty, the Kid, Margarita and the horse start the return trek to Texas. Scotty and the Kid get into another fight, in a blinding sand-storm, and the Kid tosses Scott in a ravine, and tells Margarita that Scotty has deserted them. She joins the Kid, and learns the truth about Scotty after the delirious Kid drinks from a poisoned-water hole.