Dr. David Throckmartin’s scientific expedition to the South Sea Islands discovers among ancient ruins a portal into Muria, an unknown underground world. After the disappearance of Throckmartin, his wife and two companions, his old friend Dr. Walter Goodwin enters Muria with a rescue party, only to confront an fantastic world filled with incredible beings, astounding scientific advances, and the worship of the most evil of all creatures, The Dweller. (Introduction by Mark Nelson)