The plot is set in motion when an association rejects a paper entitled "The Truth of Alchemy." The author of the paper, Mr. Karswell, does not take the rejection well. After his appeals fail, he begins to make inquiries about the expert behind the decision. The expert, Edward Dunning, soon begins to experience strange and disturbing events. He eventually becomes convinced that Karswell has placed a curse on him.
"Casting the Runes" has been adapted for film, television, and radio.
An unnamed Association has rejected a paper on "The Truth of Alchemy" submitted by a Mr. Karswell of Lufford Abbey, Warwickshire. The Secretary of the Association receives persistent and angry letters from Karswell appealing the decision. The Secretary learns from some friends who are neighbors of Karswell that the man is unsociable, easily offended, and vindictive. He is also said to practice some strange religion. He scandalized the village a few years ago by frightening the children at a magic-lantern slide show he staged. The slides and the sound effects were so realistic and terrifying that the children stampeded, many getting hurt in the process.
The Secretary recalls that Karswell published a book entitled History of Witchcraft some years ago which received terrible reviews. According to the Secretary's friends, the harshest critic, John Harrington, died under mysterious circumstances. Harrington was walking home alone at night when he apparently encountered something so terrifying that he ran and climbed up a tree. The branch broke and he fell to his death. His brother Henry has been trying to find an explanation ever since.
Shortly after the Secretary sends a firm final letter to Karswell, the expert who rejected the paper, Edward Dunning, notices a strange advertisement in a tram car. Written in blue letters on a yellow background, the advertisement reads "In memory of John Harrington, F.S.A., of The Laurels, Ashbrooke. Died Sept. 18th, 1889. Three months were allowed." Dunning brings it to the attention of the conductor. The conductor and the driver examine the strange advertisement and promise to make inquiries at the office about it.
The next evening, the tram conductor and driver come to Dunning's house. They explain that Mr. Timms at the office told them there were no advertisements matching their description. They pressed for him to come see for himself, but when they got back to the car, the advertisement was no longer there. Timms was understandably upset at the men. To clear their names, Dunning takes the note he had taken of the advertisement and goes to see Timms the following day. Timms believes him but can offer no explanations for the mysterious advertisement.
The following afternoon, Dunning is walking to the train station when a man hands him a leaflet. He glances at the blue paper and is startled to see the name of Harrington in large capitals. He stops, and a man hurries past him, snatching the leaflet away. Dunning runs back, but the man and the distributor of the leaflet are both gone.
The next day, Dunning settles down with a few volumes in the Select Manuscript Room at the British Museum. He hears his name whispered behind him and turns around, knocking some papers on the floor. Not recognizing anyone there, he picks up his papers and turns back. A stout man at the table behind him touches him on the shoulder and hands him a quire saying "May I give you this? I think it should be yours." Dunning thanks him and the man leaves the room. At the end of the afternoon, Dunning asks the assistant in charge of the room about the man. The assistant tells him that the man's name is Karswell. He also says that Karswell has been asking for authorities on alchemy, so he mentioned Dunning.
Dunning returns home feeling uneasy and finds his physician waiting for him. Dunning's housekeeper and maid have been sent to a nursing home with food poisoning. They apparently purchased bad shellfish from a hawker, although no hawker has been seen in the neighborhood. Dunning spends the evening at the doctor's home and returns late to his empty house. He is in bed when he hears his study door open. He goes out into the passage to investigate. He feels a gust of warm air, but sees and hears nothing suspicious. He goes back into his room and locks the door. Finding the electricity off, he looks for a match. Then he reaches under the pillow for his watch to check the time. His hand touches something unexpected – a hairy mouth with teeth. Dunning runs into the spare room and locks the door. He spends the rest of the night there listening for the creature to come, but nothing happens. He finally ventures back to his room in the morning and finds no signs of disturbance.
Not wishing to run into Karswell, Dunning decides not to go to the museum. He visits the nursing home first then goes to his club where he runs into the Secretary of the Association. The Secretary invites Dunning to stay with him and his wife while the servants recover, and Dunning gladly accepts the offer. That evening, Dunning tells the Secretary about his encounter with Karswell and, after much hesitation, about all the strange happenings starting with the advertisement for John Harrington. Dunning is in such a nervous state that the Secretary decides not to go into details about Harrington's death. He instead discusses the matter with his wife, and she helps make arrangements for Dunning to meet Henry Harrington.
Dunning tells Henry Harrington about his troubles and inquires about his brother. Harrington tells him that John had been in an odd state for some weeks, and he suspected that Karswell had something to do with his troubles. Three months before his death, John told Henry about a concert he attended. He lost his program and his neighbor, a stout man, gave him his copy. John was going through his concert programs later when he found a thin strip of paper inside that particular program. Henry saw the paper and thought the odd writing on it looked like Runic letters. They were discussing giving it back to the stout man at the next concert, but a warm gust of wind suddenly came in and blew the paper into the fire. Henry said "Well, you can't give it back now." After a minute, his brother replied rather crossly and inexplicably, "No, I can't; but why you should keep on saying so I don't know."
After John's death, Henry Harrington read Karswell's book on witchcraft and found a chapter on "casting the Runes" on people, mostly to get rid of them. From the way Karswell described it, Harrington felt it was written from actual knowledge rather than research. He believes that the man John met at the concert was Karswell, and the paper was used to cast the Runes on John. He feels that his brother could have been saved if he had been able to give the paper back to Karswell.
Since Karswell handled Dunning's papers at the British Museum, Harrington suggests they examine them. As they go through the portfolio, a strip of thin paper flutters out. Harrington slams the window shut just in time to prevent it from blowing outside. The writing on it is Rune-like but indecipherable. The two men agree that the paper is dangerous and needs to be returned; in person to be absolutely certain, and before the appointed day. Assuming that Dunning is being given three months, they fix the date to July twenty-third. Harrington tells Dunning that, during his three months, his brother suffered from the sense of being watched. In addition, he received two items by post. One was a woodcut, torn out from a book, illustrating a quote from The Rime of the Ancient Mariner about a man being followed by a "frightful fiend." The second item was a calendar with everything after his appointed date torn out.
Dunning and Harrington discuss plans and decide that Harrington will keep a watch of Karswell's movements. Dunning will keep the paper safe and be ready to cross Karswell's path when the opportunity arrives. Dunning's nerves are tested as May, June, and early July pass with Karswell ensconced in the safety of Lufford Abbey. With less than a week left to go, Dunning finally receives a telegram from Harrington. Karswell is preparing to travel to the Continent. He will be taking the train from Victoria Station to Dover to catch the boat. Harrington will look for Karswell and board the train at Victoria. Dunning, in disguise, will get on at Croyden West, the last stop before Dover.
As the train pulls into Croyden, Dunning spots Harrington and Karswell in a compartment. He gets on at the far end and gradually makes his way to join them. He sits down unrecognized by Karswell and begins to plot his move. Karswell's coats are piled on the seat next to Dunning, and his handbag sits open showing some papers inside. Dunning is certain, however, that it is not enough to simply hide the slip of paper in Karswell's belongings. The paper must be offered and accepted. He watches for opportunities, but Karswell is on the alert. Then finally, as Karswell gets up restlessly and goes out of the compartment, something slips off his seat. Dunning picks it up, sees it is a ticket case, and slips the paper into its pocket.
As the train approaches Dover and slows down, Karswell re-enters the compartment. Dunning manages to hand him the ticket case saying, “May I give you this, sir? I believe it is yours.” Karswell glances at it and accepts it with thanks. The carriage seems to darken and grow warm, and Karswell appears anxious. Dunning and Harrington collect their belongings and go into the corridor, and they all get off at the pier. After Karswell passes them with his porter toward the boat, Dunning and Harrington finally shake their hands and congratulate each other. Dunning is so relieved that he grows faint. Harrington helps him lean up against the wall then walks over to watch the gangway to the boat.
Karswell arrives at the gangway and shows his ticket. As he passes down into the boat, the official calls after him and asks if the other gentleman showed his ticket. Karswell asks what he means by “the other gentleman,” and the official apologizes for his mistake. Harrington overhears the official say to his subordinate that he thought there was someone else with him.
Later in their hotel room, Dunning and Harrington decide they should at least warn Karswell. Having seen his ticket in the case, Dunning knows Karswell is headed to Abbeville. He wires to hotels there a message advising Karswell to examine his ticket case.
They later learn that Karswell was killed on July twenty-third in Abbeville by a falling stone from a church tower under repair. At his estate sale, Harrington acquires a book which is missing a page where the woodcut illustration of the traveler and the demon should have been.
Night of the Demon, a 1957 British film (released as Curse of the Demon in the United States), is an adaptation of "Casting the Runes." In the movie, Karswell (played by Niall MacGinnis) is a demonic cultist with many followers. The main character, Dr. Holden (played by Dana Andrews), is an American scientist working to debunk Karswell's cult. He comes to London for a paranormal psychology conference and learns that the organizer, Professor Harrington, was killed in an accident. Harrington's niece Joanna brings the professor's diary to Holden and tries to convince him that Karswell is responsible for her uncle's death. Although a loose adaptation, the film incorporates most key elements from the short story, often in clever and creative ways. While clues to reversing the curse all come from Henry Harrington in the original story, they come in pieces from Joanna, cultists, and Karswell's sympathetic mother in the film.
"Casting the Runes" has been adapted for television twice. The first adaptation, an episode of the Mystery and Imagination British anthology series (1968), is now believed lost. A modernized adaptation was broadcast on the ITV network in the United Kingdom on April 24, 1979, as part of the Playhouse series. It was directed by Lawrence Gordon Clark who directed many of the BBC A Ghost Story for Christmas films. In the ITV version, Dunning is a female producer (played by Jan Francis) whose television series debunks claims of paranormal activities. She incurs the wrath of Karswell (played by Iain Cuthbertson) when the program features his cult.
In 1947, the CBS radio series Escape broadcast a dramatization of "Casting the Runes." The acclaimed adaptation follows the short story very closely, but with two additional scenes designed to scare the audience. The ending is also made more suspenseful with the action taking place on Dunning's "last day."
"This Will Kill You" (1974), an episode of the CBS Radio Mystery Theater series, is an uncredited loose adaptation of "Casting the Runes." In the unsuspenseful dramatization, the main character becomes convinced he is under a spell after developing an inexplicable sense of fear. He visits an expert on the occult who quickly connects his problem to the author of the book he critically reviewed. It is the appointed date of the "death curse" which is written in Runic letters, and the expert explains to the victim how to pass the paper and the curse to someone else.
A 15-minute radio play based on "Casting the Runes", starring Mark Gatiss as M.R. James, was first broadcast on BBC Radio 4 on in the United Kingdom on December 18, 2018 a"s the second episode of the five-part mini-series The Haunting of M.R. James.
- The BBC series A Ghost Story for Christmas consists of twelve TV movies that were first shown on British television between 1971 and 2013. Of the twelve, two are original stories. The rest are adaptations of the short stories "The Stalls of Barchester Cathedral", "A Warning to the Curious", "Lost Hearts", "The Treasure of Abbot Thomas", "The Ash-tree", "A View from a Hill", "Number 13", "Oh, Whistle, and I'll Come to You, My Lad", and "The Tractate Middoth" by M.R. James and the short story "The Signalman" by Charles Dickens.
- The other episodes of The Haunting of M.R. James are based on "The Mezzotint", "The Stalls of Barchester Cathedral", "A Warning to the Curious" and "Rats".