Coblentz’s subterranean adventure novel tells the story of mining engineers Frank Comstock and Philip Clay who, after being presumed dead in a mine collapse, find themselves trapped in a vast, hidden underground world filled with strange creatures, advanced civilizations, and mysterious lights, where they must navigate perilous situations and grapple with the concept of a whole society living beneath the Earth's surface, far beyond the knowledge of the surface world.
The novel opens with Frank Comstock recounting the catastrophic mine collapse that led him and Philip Clay to fall into the hidden underground realm. As they explore, they encounter strange sounds, glowing lights, and evidence of an advanced civilization that has developed its own technology and culture. Frank is captured by a group of pale-faced underground people, who are initially suspicious of his presence but eventually decide to study him and his "primitive" world.
Professor Tan Torm, a leader of the underground society, assigns his daughter Loa to teach Frank their language, leading to a romantic subplot. Frank struggles to adapt to the customs and physical standards of the underground society, which values a different type of beauty than the surface world.
"In Caverns Below" was first published as a serialized novel in the March, April, and May 1935 issues of "Wonder Stories." It was later reprinted several times in book form, as well as in the Fall 1950 issue of “Fantastic Story Quarterly.” Later editions were also published under the title “Hidden World.” The novel is now available online at Project Gutenberg under its original title.
