The Phantom Empire is a 12-episode movie serial by Mascot Pictures, starring the singing cowboy Gene Autry.

After the ancient continent of Mu gets buried under the ocean, some of the Muranians manage to survive and continue their existence beneath Autry’s dude ranch while developing technological tools like televisions and producing ray guns. When the peaceful existence of the Muranians gets interrupted by a group of crooks living above ground, Autry tries to prevent a war from breaking out between two groups in order to keep his Radio Show on air.