West to Glory (1947)

At a border town, Eddie Dean and his partner, Soapy Jones, attend a fiesta at the home of Don Lopez who, in accordance with his custom, displays a valuable diamond necklace to his guests and has one of them, Maria, wear it. Jim Barrett, another guest, offers to buy the necklace but Don Lopez declines to sell. Barrett, with his henchmen Corey and Avery, plan to steal the necklace and the rest of the Lopez diamonds. Maria, to Eddie's surprise, appears to be working with the outlaws. But, as Eddie's investigation proceeds, it develops that Barrett's gang has also robbed Don Lopez of his gold, and that Maria is a representative of the Mexican government, sent to protect the gems.