Gridley is mining silver from an old Mexican mine and bringing it into the USA thru a passage into his worthless mine. Border guard Rogers suspects Gridley and finally finds the secret entrance to the Mexican mine. He sends Lee Madison for help only to have her captured by Gridley. Trigger brings help that takes care of Gridley's men and now Roy has to rescue Madison.
The usual, routine, singing cowboy stuff from Roy Rogers as he is sent to investigate some shenanigans at a ranch on the US/Mexican border. The film really belongs to Andy Devine as "Sheriff Cookie"; the enthusiastic, if not desperately competent local sheriff who alongside trashy-journalist "Lee Madison" (Dale Evans) has to help Rogers get to the bottom of it all. Fritz Lieber adds a wee bit of weight to the proceedings, and if you like songs with your westerns then this is no better or worse than the norm. The story is way too thin for 80 minutes though, an hour would have sufficed.