Thomas Carnacki is not a typical detective; he investigates the "ab-human" using a combination of ancient folklore and electrical gadgetry. These stories introduce the "electric pentacle" as a defense against the outer dark, blending the Victorian ghost story with a modern, almost scientific approach to the supernatural. The cases range from genuine hauntings to clever frauds, all narrated in the comfortable safety of a smoking room. It is a unique collection that treats the paranormal as a dangerous natural force to be understood and contained.