The Unknown Ranger (1920)

A man named Chandler, claiming to be a novelist in search of local color, arrives at a town near the Mexican border, where he makes advances toward Jo, a girl living a solitary life on a desert ranch. Manning, a cowboy, suspects Chandler's motives, and his suspicions are strengthened when Chandler is caught cheating at cards. Following a gang of Mexicans to their mountain retreat, Manning learns that Chandler and the Mexicans are smuggling opium across the border. Two gang members are killed in the ensuing fight, but Chandler, wounded by Manning after a chase on the cliffs, escapes to Jo's home, where he denounces Manning as a smuggler. Manning arrives and dispels Jo's misgivings about him by revealing that he is a Texas Ranger, sworn to secrecy.