Sunset Serenade (1942)

After a wealthy rancher dies, disgruntled employee Vera Martin (Joan Woodbury) and neighbor Gregg Jackson (Onslow Stevens) concoct a scheme involving a counterfeit mortgage and the drastic re-routing of a nearby river in an attempt to take control of his estate. When the rancher's only living heir -- a baby -- arrives from New England, his nanny, Sylvia Clark (Helen Parrish), falls victim to the crooked duo. A desperate Clark turns to heroic gunslinger Roy Rogers (Roy Rogers) for help.