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

The Queen orders Gene to tell her who saved him, but he refuses; after Gene sees the kids, he tells the Queen that it was Argo; the Queen is shocked, but forms an alliance with him and orders death to Argo.

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

(Chapter 5)

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.