Randolph Scott stars in this adequate Zane Grey adaptation. Lawman Larry Sutton (Scott) is assigned to solve a series of murders occurring at a radium mine. Among the suspects is mine owner Mrs. Borg, played by legendary Broadway star Leslie Carter in a rare film appearance. The key to the mystery would seem to be a sinister Chinese gent named Ling Yat (Willie Fung), but he proves to be one of many red herrings. Hoping to beat Sutton to the solution is local sheriff Tex Murdock, played by veteran vaudevillian Chic Sale. With so much high-powered talent, it's small wonder that many reviewers failed to mention the ingenue, a young actress named Anne Sheridan. A remake of the 1922 film Golden Dreams (the original title of the Zane Grey novel), Rocky Mountain Mystery was reissued as Vanishing Pioneer.