The Child of the Cavern follows engineer James Starr as he receives a letter from an old friend and co-worker, Simon Ford, requesting that he revisit a depleted coal mine in Scotland that he used to manage. Upon arriving, Starr finds the entire Ford family living in the mine, and Ford explains that a new coal vein has been located. Soon after Starr’s return, however, strange events start to occur, which seem to be supernatural. After a startling discovery, the characters continue to investigate these occurrences over the course of several years.