In the decadent underworld of Victorian England, a mad scientist’s experiment unleashes a horror beyond comprehension. Dr. Raymond, obsessed with the idea of seeing the “Great God Pan,” the pagan deity of nature and sexuality, performs brain surgery on a young woman named Mary. The surgery succeeds, but at a terrible cost. Mary is driven insane by the visions of the supernatural world that she now sees, and she becomes the vessel for a malevolent force that threatens to destroy all in its path.

Meanwhile, a series of mysterious and disturbing events begin to plague the city. People are vanishing without a trace, and those who remain are gripped by a growing sense of terror. As the body count rises, a group of investigators must race against time to uncover the truth behind the madness.

But what they discover is more than they could ever have imagined. For the Great God Pan is not a mere myth or legend. It is a real and terrifying being, and it has come to claim our world.

As the inspiration for several influential horror artists such as H.P. Lovecraft, Stephen King, and Guillermo del Toro, The Great God Pan is a highly influential work of literature that has had a significant impact on the horror genre and on popular culture in general, serving in lasting memory as one of Arthur Machen’s best works.