Prof. Ewart Masters spends his convalescence, following a car accident, at the home of his nephew Jason Masters, pursuing his studies of ancient civilizations, during which he makes startling discoveries about the hidden city beneath the Yorkshire moors. His search to unravel the mystery of the green figurines, his efforts to assess the implications of Robert Krug's manuscript, lead ultimately to Devil's Pool and the surviving world of Lh'yib, culminating in a series of dream-like adventures as he wanders through the nightmare corridors of his new environment.

Beneath the Moors is primarily Gothic in atmosphere, its brooding mystery and stark terror occasionally relieved by bits of quiet charm and subtle humor. And the author's straightforward "autobiographical" technique possesses an element of immediacy seldom achieved in this type of narrative.