Río Escondido (movie, 1948)

Called by the Mexican President himself, and in spite of a heart condition, young teacher Rosaura Salazar travels to the deserted town of Rio Escondido to accomplish the mission of bringing education to the poorest people. Being there, Salazar has to fight Regino Sandoval the evil landlord of the town. He has transformed the town into his own property, imposing his will and spreading death everywhere.