|Gene Autry||Gene Autry|
|Frankie Darro||Frankie Baxter|
|Betsy King Ross||Betsy Baxter|
|Wheeler Oakman||Lord Argo|
|Charles K. French||Mal|
Gene is a singing cowboy happily running a radio station that happens to be located just above a mystical subterranean city. Conniving scientists discover the city and its rich deposits of radium ore and make plans to invade the underground world -- but first they must knock Gene out of the picture. The cowboy is not easily discouraged, however, and he enters the depths with his young sidekicks Frankie and Betsy in order to set things right.