A singing cowboy stumbles across an ancient underground civilization beneath his ranch.

After defeating the guards, Gene reaches the surface and takes Beetson's airplane; the Queen kills the engine.

The Baxters find Gene in time to save him; Argo orders the death of all surface people; battling, Gene arrives at where the Queen is being executed, but is knocked into the path of death-dealing rays.

(Chapter 5)

Gene tries to stop the radium bomb sent by the Queen to kill the riders on the surface.