A treasure hunter discovers a hidden, ancient civilization deep within the Andes, triggering a conflict between primordial forces. Nicholas Graydon, a prospector seeking gold in the South American wilderness, encounters a subterranean realm where time and evolution have diverged from the surface world. He becomes entangled in the struggle between the Snake Mother, a deity-like figure of wisdom and reptilian heritage, and the Lord of Evil, a malevolent entity seeking to dominate this forgotten domain. The narrative follows Graydon as he navigates the physical dangers of the cavernous environment and the complex political landscape of a society that defies conventional human logic.

Readers frequently highlight the imaginative scope of the world-building, noting that the author prioritizes visual atmosphere over rigid realism. Discussion often centers on the unique depiction of the Snake Mother, which remains a distinct element of the fantasy genre. Critics observe that the pacing reflects the pulp traditions of the era, balancing rapid action sequences with descriptive passages of the environment. The work is often cited for its influence on the development of the lost world subgenre, providing a template for subsequent writers in the field.