The Undertaking have their base on Egdon Heath, the fictional moorland in the works of Thomas Hardy.
In one of the Sherlock Holmes stories, Watson mentions the unsolved case of "Isadora Persano, the wellknown journalist and duellist, who was found stark staring mad with a matchbox in front of him which contained a remarkable worm, said to be unknown to science." In this series, Persano was a Great Enchanter defeated by the Diogenes Club and their allies in 1903, and he and the worm were taken into custody by the Undertaking. The worm was a sapient alien life-form, and apparently of the two it was the brains of the operation.
The idea of a worm being the "brains" of an evil plot is a shout-out to Captain Marvel villain Mr. Mind.
Sir Henry Merrivale is mentioned as another member of the Diogenes Club.note Which he actually was in his own canon, because his creator was Sherlock Holmes fan.
Dr. Martin Hesselius (the occult detective created by Joseph Sheridan Le Fanu) and Dr. John Silence (an occult detective created by Algernon Blackwood) are mentioned among those who took an interest in Rose Farrar's disappearance.
After fending off a monster with a crucifix, Sir Arthur says he tried it because the creature's fangs had reminded him of Dracula.
When Crowley expounds his theory of what's going on, Catriona accuses him of ripping off the plot of The Great God Pan.
The combination of fair folk and things happening because people believe in them leads Catriona at one point to think of Peter Pan.
Charles mentions owning a copy of De Vermis Mysteriis, a grimoire from the Cthulhu Mythos.
Charles's library also includes an edition of The Collected Poems of Jeffrey Aspern, the central character of Henry James's The Aspern Papers.
The goblins lure Dickie into a trap with a trail of Clues that include "a dish of butter with a sprig of parsley sunk into it, a dead canary bleached white, a worm unknown to science" (references to Noodle Incident untold cases from the Sherlock Holmes stories) and "a cigarette end with three distinctive bands" (the signature of the custom-made cigarettes smoked in real life by Ian Fleming and in fiction by James Bond).
The author George MacDonald and the artist Arthur Rackham are mentioned as other people whose fictional creations have been influenced by the Fair Folk.
Some of Dickie's family call him "Hawkshaw", after the detective in the 1863 play The Ticket-of-Leave Man whose name became a byword for "detective" the way "Sherlock" did for later generations. The narration implies that Hawkshaw actually existed in-universe.
Inspector Mist is said to be part of the Bureau of Queer Complaints. This is a reference to a book written by John Dickson Carr, which was adapted in the fifties into a TV series called Colonel March of Scotland Yard.
The Diogenes Club's "Green Ribbon Files", cases deemed unsolvable and placed where people will hopefully forget about them, are a reference to The X-Files.
Barbara Corri got her college education at the same fictional Oxford college as Harriet Vane.
The Man Who Got Off the Ghost Train
The express train's colorful history includes a notorious incident involving Colonel Sebastian Moran. The details are different, but this is a shout-out to Terror By Night, in which Moran is the villain, and which is likewise set on an express train to Scotland with a MacGuffin the heroes are guarding.
Richard's internal monologue namedrops a few former club members, among them Adam Adamant and a few early occult detective characters: Flaxman Low (works of Hesketh Hesketh-Prichard), the Incredible Robert Baldick (created by Terry Nation), and Cursitor Doom (Smash! comics).
Richard Riddle, Boy Detective in "The Case of the French Spy"
There's a maritime mystery involving a ship called the Sophy Briggs, which is a double reference. One of Sherlock Holmes's untold cases involved a ship called the Matilda Briggs, and Sophy Briggs was the youngest of the passengers who disappeared mysteriously from the Mary Celeste. Also, Holmes describes the case of the Matilda Briggs as "a story for which the world is not yet prepared", and the protagonist of "The Case of the French Spy" describes his own adventure the same way.
Violet quotes from Rudyard Kipling's "A Smuggler's Song" — which is a neat trick, because the story is set during the Second Boer War and Kipling didn't publish the poem until several years after the war ended.
References to the Cthulhu Mythos: Violet speculates that the Fish Person is from "Atlantis or Lyonessse or R'lyeh", and the only word of the Fish Person's language that's transcribed is "f'tagn" (which Dick suspects is a swear word).
When Catriona is trying to guess why the Diogenes is getting involved in a murder investigation, one of her guesses is that it was committed via "the venomous bite of a worm unknown to science". An unsolved case involving "a remarkable worm, said to be unknown to science" is mentioned as a Noodle Incident in the Sherlock Holmes story "The Problem of Thor Bridge".
One of the Splendids' old adventures involved fighting "terror lizards" in Maple White Land. Maple White Land is the South American plateau with the remnant dinosaur population that is the setting of Arthur Conan Doyle's The Lost World.
The endurance stunt the Mystic Maharajah attempts near the end of the story is a parody of the endurance stunts done by stage magician David Blaine, particularly the "Above the Below" stunt he did in London in 2003.
The title of the story is a reference to the non-fiction book Clubland Heroes by Richard Usborne, an influential work of British pop-culture criticism studying the work of John Buchan, "Sapper", and Dornford Yates, arguing that they were the most significant examples of a wider school of inter-war British thriller marked by Rich Idiot With No Day Job or Gentleman Adventurer heroes, espionage-related content, and frequently right-wing and, by today's standards, very bigoted political views.
The warden of the Extranormal Prison mentions "the Lake LaMetrie elasmosaur", from "The Monster of Lake LaMetrie" by Wardon Allan Curtis.
Geneviève's alias of Geneva Deodati is a reference to the Villa Diodati in Geneva, Switzerland, which holds a special place in the history of horror because it's where Mary Shelley came up with the idea for Frankenstein and Polidori came up with The Vampyre.
Carnacki the Ghost-Finder and Doctor Nikola (a supervillain created by Guy Boothby) are named among the people who joined forces to help defeat Isadore Persano.
Characters who have been refused association with the Diogenes Club due to being unprofessional and/or excessively violent include Abraham Van Helsing, Bulldog Drummond, and Michael Bellamy (from The Green Archer by Edgar Wallace).
Geneviève compares Zenf to Napoleon, Dracula, and the Beetle. The Beetle was a horror novel by Richard Marsh that came out the same year as Dracula and was initially the bigger hit.
Margery Device's surname is a historical shout-out: several women with that surname were among the accused in the Lancashire witch trial of 1612, one of the largest and most famous witch hunts in English history.
Sherlock Holmes's nemesis Professor Moriarty is mentioned a couple of times, once to compare Zenf to him, and once while describing Sorcerer's professional qualifications as an astronomer; apparently he debunked Moriarty's famous work The Dynamics of an Asteroid, which according to this story predicted that said asteroid was on a disastrous collision course with Earth.
The official portrait of Mycroft in Charles's office was painted by Hallward, the artist who painted The Picture of Dorian Gray. Charles comments that he feels "the artist had not, in this case, truly captured his subject's soul."
One of the guests at Margery's party is wearing a pair of ruby cufflinks made from the eyes of a golden pagan idol, a reference to "The Green Eye of the Yellow God" by J Milton Hayes, in which an Englishman steals one of the emerald eyes of a pagan idol and suffers a terrible fate.
Mycroft's contingency plan for dealing with Zenf has the subtitle "With Notes Upon the Segregation of a Great Enchanter". After his retirement, Sherlock Holmes wrote Practical Handbook of Bee Culture, with Some Observations upon the Segregation of the Queen.
Students mentioned in passing during the story include an American girl named Tish Frump, another American named Janice Marsh (of the Innsmouth Marshes) and a girl named Sally Nikola with a notorious father (implied to be Guy Boothby's Dr Nikola).
Another student is named ten Brincken, and was reportedly grown rather than born. This is a reference to the 1930's German film Alraune (the girl in question also appears in Angels of Music).
One of the Black Skirt trios are given the collective nickname of "the Ghidorah".
When Amy learns about Paquinget's Green Thumb, she wonders if there's a plant-themed other dimension called the Green to go with the Purple that is connected to several of the other Unusuals' abilities. In Swamp Thing, the existence of the Green is a major plot point.
At one point, the werewolf girl Gould is described as having her eyes bulging in astonishment "like the Big Bad Wolf in the fairy tale". It's actually a shout-out to the animated film "Red Hot Riding Hood", which the narration can't reference directly because it wasn't made until after when the book is set.
Another Sherlock Holmes reference: Moria Kratides is the daughter of Sophy Kratides from "The Greek Interpreter".
When Knowles is recounting what she's learned about the history of the Broken Doll, part of it is an untold adventure of Carnacki the Ghost-Finder.
Knowles uses an Electric Pentacle, Carnacki's signature protective device, in the confrontation at the Music Room, and it proves capable of suppressing the telekinetic powers of both Amy and the Broken Doll.
Alternative Title(s):The End Of The Pier Show, Angel Down Sussex, The Gypsies In The Wood, Clubland Heroes, Sorcerer Conjurer Wizard Witch, The Secrets Of Drearcliff Grange School, The Haunting Of Drearcliff Grange School