"John Silence: Physician Extraordinary" is a collection of stories written by Algernon Blackwood. The book revolves around a character named John Silence, who is a doctor with extraordinary psychic abilities. He is known for his ability to investigate and solve paranormal mysteries that cannot be explained by conventional science. The book comprises six stories that feature John Silence as the main character. In the first story, "A Psychical Invasion," John Silence investigates a case of a woman who is being haunted by an evil spirit. In the second story, "Ancient Sorceries," he travels to a remote French village to investigate the strange behavior of its inhabitants. In the third story, "The Nemesis of Fire," John Silence investigates a case of spontaneous human combustion. In the fourth story, "Secret Worship," he travels to a remote English village to investigate a cult that is performing human sacrifices. In the fifth story, "The Camp of the Dog," John Silence investigates a case of a haunted tent in the Scottish Highlands. Overall, "John Silence: Physician Extraordinary" is a collection of eerie and supernatural stories that showcase the extraordinary abilities of the titular character.