The book is an expanded version of the novelettes "Gunpowder God", which had been published in the November 1964 issue of Analog Science Fiction and Fact, and "Down Styphon!

"Gunpowder God" itself is a Paratime-series rewrite of the unpublished story "When in the Course", which takes place in the Terro-Human Future History milieu.

This alternate North America is split up into a number of kingdoms, each composed of small principalities, with a level of technology roughly equivalent to that of the late European Renaissance.

Ptosphes' overlord, Great King Kaiphranos of Hos-Harphax, refuses to intervene because the priests of the god Styphon want Hostigos to be destroyed.

With his understanding of military strategy and tactics, he reorganizes the outnumbered Hostigos army and repulses Nostor, capturing an important border town in the process.

Vall takes a liking to the resourceful Kalvan and realizes that his brother policeman has fabricated a background for himself, one that motivates him to conceal the Paratime secret.

Sarrask of Sask is captured and agrees to become a vassal of a new Great King after he learns that he can share in the looting of Styphon's lavish temples.

At first, Kalvan proposes that his future father-in-law assume the new throne, but Ptosphes refuses, stating that the other princes would never stand for being ruled by someone they view as an equal.

Carr further continues the storyline with the novels Kalvan Kingmaker, Siege of Tarr-Hostigos, The Fireseed Wars and the forthcoming The Gunpowder God (which shares the same title as the original novelette).