Billy, after shooting down land baron William Donovan's henchmen for killing Billy's boss, is hunted down and captured by his friend, Sheriff Pat Garrett. He escapes and is on his way to Mexico when Garrett, recapturing him, must decide whether to bring him in or to let him go.
When the ancient continent of Mu sank beneath the ocean, some of its inhabitant survived in caverns beneath the sea. Cowboy singer Gene Autry stumbles upon the civilization, now buried beneath his own Radio Ranch. The Muranians have developed technology and weaponry such as television and ray guns. Their rich supply of radium draws unscrupulous speculators from the surface. The peaceful civilization of the Muranians is corrupted by the greed from above, and it becomes Autry's task to prevent all-out war, ideally without disrupting his regular radio show.
Re-edited feature version of serial The Phantom Empire (1935). Singer Gene Autry discovers a race of advanced humans living beneath the earth.
