A controversial scientific experiment opens the door to realms beyond human comprehension, unleashing terrifying consequences. As a trail of inexplicable deaths and madness spreads through London's upper class, a determined investigator pieces together clues that point to an ancient, otherworldly presence. When the horrible truth is finally revealed, it challenges everything believed about the nature of reality and humanity's place in the universe. "Of Mr. Machen's horror-tales the most famous is perhaps 'The Great God Pan' (1894) which tells of a singular and terrible experiment and its consequences."-H. P. Lovecraft