Quicksands (1923)

Stationed at the Mexican border, a young lieutenant whose job is to capture a ring of narcotics smugglers, spies his sweetheart, the daughter of a U. S. Customs official, in a cantina suspected of being the headquarters of the dope ring. Believing that she is part of the ring, he decides to resign his job. Word arrives that the girl and her father are being held prisoners by the gang. The lieutenant goes to aid them and is captured. Finally, the U. S. Army rescues the trio and the girl is revealed to be a secret agent.