Locked Room Transcript

Caroline: The line between crime fiction and the supernatural can get a little blurry at times. Although the “rules” of fair play in detective fiction popular in the 1920s and 30s prohibited the inclusion of ghosts, demons, and other paranormal phenomena, writers still enjoyed teasing their readers with murder scenarios that, at first glance, appeared impervious to rational explanation.

The best expression of this facet of the classic whodunnit is the locked room mystery. A body is found in a sealed chamber, definitely murdered, but there is no way the culprit can have got in or out. How did the murderer reach the victim and then escape again? Right from the very beginnings of detective fiction in the nineteenth century, this scenario has fascinated writers and readers alike.

That’s why, today, we’re going to learn how to solve impossible crimes.


Welcome to Shedunnit. I’m Caroline Crampton.


Like a lot of things about detective fiction, the origins of the locked room mystery can be traced all the way back to Edgar Allen Poe.

Jim: I think there’s a common conception that the first impossible crime story was also probably the first crime story, which is widely accepted to be “The Murders in the Rue Morgue” by Edgar Allen Poe from 1843. I think this comes about because of the need for investigation being so key to the impossible crime, to have somebody to actually look into it, to come to some degree of rationalisation why this problem is involved.

Caroline: This is Jim Noy, an impossible crime enthusiast and the author of the detective fiction blog The Invisible Event. He’s something of an expert on this subject, which is why I’ve called him in as our consulting detective on this case. Before we go any further with Poe and the rest, though, I think we need to work out exactly what we mean when we say “impossible crime” or “locked room”. Luckily, Jim is much better at defining these phrases than I am.

Jim: I think there are a couple of phrases they are used interchangeably, I think people talk about locked rooms and they talk about impossible crimes and they also talk about miracle problems. And I tend to refer to them as impossible crimes. I think a locked room is a type of impossible crime web, something occurs inside of a locked room, but typically an impossible crime is usually a crime, a criminal act. It’s usually a crime has been committed in such a way that upon its initial presentation to the characters in the story and certainly to the reader, it doesn’t seem physically possible. And I suggest that beyond that, it also needs to remain to appear physically impossible for a very basic level of investigation and so to a very sort of key initial appearance there must also be that element of bafflement of how it has been committed.  

Caroline: So a locked room murder and a miracle problem are both types of impossible crime — the latter being a situation that appears physically impossible but that isn’t actually a crime like a murder or a theft, such as a sudden manifestation or disappearance. And, as Jim says, it isn’t enough for a writer merely to construct an impossible-seeming scenario, if as soon as the detective steps through the door, they’re going to immediately understand how it was done. The impossibility needs to withstand at least some investigation to really earn the label. So, back to Poe, who did this first. Or did he?

Jim: I mean the earliest cited example is from the Book of Judges in the Bible, where an incredibly fat man is run through with a sword in such a way that their assailant finds it impossible to remove the sword from the wound. And so when people enter the room it would appear to be someone is found killed in a locked room, there’s no sign of the weapon. It just so happens that the weapon is lost inside of the oversized body. There’s also from the writings of Herodotus from about 440 B.C. There’s a story called Rhampsinitus and the thief, which is about a thief who has found a way to gain access to a very rich man’s store of gold. From the reader’s perspective, we know how the access is achieved, but from the man being stolen from it it appears to be impossible.

Caroline: Plenty of Gothic and sensation fiction also dabbles with seemingly impossible incidents, but the crucial point is that it’s not until Poe in the mid nineteenth century that we get the character of C. Auguste Dupin trying to solve these impossibilities in a manner that we now recognise as a kind of detection.

Although it’s been more than a century and a half since “The Murders in the Rue Morgue” was first published, I don’t want to spoil its solution for you — I strongly recommend you go and read it, and I’ve put a link to a free online edition in the show notes. In many ways, it’s a foundational text of detective fiction, even if Dupin doesn’t call himself a detective or describe what he’s doing as “detection”. In fact, the earliest citation for the word “detective” in the Oxford English Dictionary is, like Poe’s story, from 1843. The concept of rational investigation as a part of either professional policing or private sleuthing was really in its infancy.

Over the next few decades, detectives in both real life and fiction proliferated. In detective stories, locked rooms and other kinds of impossible crime became gradually more common, with more and more writers starting to experiment with them.

Jim:  By that point you’ve also got the work of L.T. Meade and Robert Eustace starting to come out. Robert Eustace is possibly best known to Golden Age detective fans as the man who wrote the Documents in the Case with Dorothy L. Sayers. But he and L.T. Meade wrote a series of short stories, I believe, under the title The Master of Mysteries, some of which are impossible crimes, some of which are incredibly auric, most of which are incredibly hoary.

Caroline: Meade was an incredibly prolific Irish writer who produced over 300 books in her lifetime. For those who enjoyed the Victorian Pioneers episode of the podcast about early lady detectives, Meade is also worthy of note as the co-creator of several significant female sleuths and villains, including Florence Cusack and Madame Coluchy. Through her work with Eustace, she made a substantial contribution to the emerging impossible crime subgenre, too.


1892 is an important year for locked room mysteries. There were two publications this year that matter to the investigation we have at hand — one of which I expect a lot of you will have heard of, another that I suspect might be a little more obscure.

Jim: There is the Speckled Band by Arthur Conan Doyle from 1892, where a woman is found killed in what is essentially a locked and sealed room. You also have from 1892 The Big Bow Mystery by Israel Zangwill, which is another incredibly famous example, which is probably rightly famous because of, again, the fact that it comes up with a very interesting and I believe at the time original solution. But also what it comes up with is a false solution. And so Zangwill arguably in the history of impossible crimes, introduced the idea of a false solution, where what you have is a series of events that would appear to explain away the situation, which are then shown typically in the final chapter to be inaccurate for whatever reason.

Caroline: Arthur Conan Doyle might be by far the most famous late Victorian detective writer, but he was by no means the sole practitioner of the impossible crime story.

Jim: So certainly by the time Doyle is writing these with Holmes, it’s not as if he’s alone in it and it’s not as if nothing has been done in the subgenre by that point. I think it again, in much the same way that Poe and Rue Morgue is so incredibly famous and so it’s seen as the star of the genre. Holmes is so rightly incredibly famous that is often seen as the next logical step of really anything post about 1850.  

Caroline: In the early twentieth century, several writers notably picked up the thread of the impossible crime and tried to experiment a bit further with it.

Jim: In the early 20th century, you’ve got Jacques Futrelle who wrote to say, I mean, Futrelle died on the Titanic in 1912, so probably about 1904, 1905, you got Jacques Futrelle writing his Thinking Machine stories. You’ve got Edgar Wallace writing The Four Just Men around about the same sort of time.

Caroline: The thing about Futrelle, Wallace and other very early twentieth century impossible crime writers, though, is that when you read their stories now, they don’t seem that impossible. Sometimes, it’s even downright obvious what the big reveal is as soon as you’ve read the initial setup. And that’s because these solutions often rely on a general lack of understanding of scientific, medical or technological principles in the reading public of the day.

Jim: And what happens in this era is the rationalisation of the seemingly inexplicable by things which I think at the time weren’t necessarily appreciated by the populace. So we now in 2020 are broadly able to take for granted a lot of scientific principles, a lot of medical principles that I don’t think 100 hundred years ago would have been quite as appreciated by the man and woman in the street

Caroline: As writers sought to outdo each other and their readers with more and more outlandish impossible crimes, the plausibility of what they were writing about started to fall away. For instance:

Jim: Wallace, when he wrote The Four Just Men was he was relying on a scientific principle, which was relatively new at the time, but which if you had a certain amount of insight and understanding, you could actually anticipate. You go back to “The Murders in the Rue Morgue” — there’s been some fantastic critiques of Murders in the Rue Morgue where the physical space just doesn’t make any sense. It’s not physically possible for what is supposed to have occurred in that space to actually have occurred. It relies on, amongst other things, the existence of a secret hidden catch to seal the window from the inside. It would only exist if the person putting that window in the building knew that in some point in the future, that window was going to be featured in a baffling locked room murder like there is a meta element to it that just becomes so, so incredibly preposterous.

Caroline: The boundary between what is an impossible crime story and what is a science fiction story has always been a bit porous — and that’s something we’ll talk about in more detail a bit later in this episode. But before the locked room murder mysteries of the 1900s and the 1910s could any more implausible, an important shift occurred. And the pivotal writer here? Well, it’s G.K. Chesterton.

Jim: You get to someone like Chesterton and we’ve gone through an era of a lot of bogus, false, scientific, in inverted commas, reasoning, being used to explain away impossible crimes. You go through a lot of principles of, you know, weird physical spaces may be or may not have the properties that describe the fact that, you know, we just accepted that every single building older than a certain age has at least eleven hidden passages leading into any particularly spooky room. But crucially, what Chesterton does and this is one of the things I really love about his writing, is that Chesterton starts to move away from the scientific principles, from the physical principles, and starts to move into the psychological principles. And so it starts to look at the reason that something might be apparently impossible, not necessarily being because there’s something about the physical space or because there’s some scientific principle that people are ignorant of, but fundamentally because that there is a key human blindness in the way that people perceive situations.

Caroline: Chesterton was, in a way, a literary godfather to golden age writers like Dorothy L. Sayers, Anthony Berkeley, Agatha Christie and many others. As I mentioned in the recent episode about the Detection Club, this status was confirmed when he was asked to be the club’s first president in 1930. The first story featuring his priest-detective Father Brown, The Blue Cross, was published in 1910, and he wrote over fifty more over the next two decades. And there’s one from 1911, that expresses his psychological take on the impossible crime better than any other.

Jim: Now, there’s one story in particular that leans into this very heavily, “The Invisible Man“. And I detest that story with every fibre of my being. But it’s fascinating from the perspective of how heavily it leans into a psychological principle. He started to use these psychological principles and started to expand up from just the use of physical space and just the use of what you can physically see in a room to this point of you don’t see this not because of the physical space, but because of you, because there is an inherent flaw in the observer in the way in which these events are interpreted by people in the narrative.

Caroline: The invisible man isn’t invisible because of some special serum he’s drunk or because of some clever trick with a mirror, but because the unreliable, flawed people observing him are can’t see him. I’m not a huge fan of Chesterton or Father Brown either, but there can be no doubt that by popularising the idea of the unreliable narrator and witness, he helped move the impossible crime story into its next, and arguably greatest, phase.

After the break: the golden age of locked rooms, and beyond.

Ad music

The impossible crimes of the golden age are at once both simpler than their predecessors and more complicated. There’s far less reliance on elaborate window catches, fake panels in the wall and untraceable poisons, and instead the author has to construct the impossibility so that it exists in the eye of the beholder, as it were. No more physical slight of hand or improbable trickery.

Jim: It’s this idea that you want your reader to engage and so you almost want to be able to hold up to them the physical evidence almost verbatim. I think that became the key principle of what we now talk about as the golden age. 

Caroline: This where we can consider impossible crimes as part of the bigger trend for fair play that is so fundamental to the mechanics of golden age detective novels. It’s not fair if the solution to the impossible crime turns out to be a previously unmentioned secret passage; it’s also much more fun if the reader has known the secret passage was there the whole time but just didn’t work out what it had to do with the plot. This need to lay out all the physical restrictions up front is also where we start getting one of my favourite things about crime novels from this period: the maps in the front of the book.

Jim: The understanding of the physical geography of the space really had to improve, and so you start to see an upswing in the use of maps. And there is a story, “The Round Room Horror” by A Demain Grange from about 1911, which is slightly pre golden age. But this is the earliest example I’m aware of where the precise physical measurements of a space really matter. But because something has a particular dimension, a physical act is is possible inside of that space, then explains away the impossible crime. It’s the first example, the earliest example I’m aware of of a diagram of the space being provided in such a way that the exact arrangement of things in that space really matters.

Caroline: As with all detective fiction that abides by the precepts of fair play, the whole point of this era of impossible crime stories is that the writer gives the reader everything that they need to guess whodunnit, but then still managed to fool them in the end. In that sense, writer and reader are competing with each other, tussling over who is going to triumph by the time the denouement rolls round.

Jim: There’s no longer any fun setting a puzzle that no one else but me can solve. Authors really wanted it to be solvable. You know, John Dixon Carr called the writing of impossible crime fiction, the grandest game in the world. And I mean, the whole point of a game is that you want people to be able to play it. 

Caroline: It’s impossible to talk about golden age impossible crimes without talking about John Dickson Carr. Although born and raised in the United States, Carr is usually grouped in with the mostly British group of writers who dominated detective fiction in the 1920s and 30s. In 1932 he married an Englishwoman, Clarice Cleaves, and they settled in London, where Carr set to work publishing mystery novels at a great rate. In 1933 he published his first novel featuring the academic and amateur sleuth Dr Gideon Fell, Hag’s Nook, and then in 1934 under the pseudonym Carter Dickson he published The Plague Court Murders, a brilliant locked room murder mystery featuring amateur sleuth Sir Henry Merrivale. He carried on working with both of these pen names and detectives for several decades, publishing dozens of novels.

Jim: John Dixon Carr is the greatest practitioner of impossible crimes in the golden age. He wrote an astonishingly large number of brilliant crimes, came up with some brilliant solutions, came up with some brilliantly original solutions, came up with some brilliant twists on extant solutions, really folded the machinations required for the impossibilities into his plots incredibly well. Used Chesterton’s principles of psychology brilliantly. I mean, read something like The Problem of the Green Capsule, which is also known as the The Black Spectacles from 1939. I think that is pretty much the pinnacle of the impossible crime in Golden Age detective fiction, I think, is probably the pinnacle of golden age detective fiction. 

Caroline: That’s a pretty strong endorsement, and Jim definitely knows what he’s talking about. Carr was constantly innovating, looking for new takes on the already well known tropes of the impossible crime. In that book The Problem of the Green Capsule from 1939, a wealthy man sets up an experiment to prove that there’s no such thing as a reliable eyewitness. He stages a number of scenarios before a group of witnesses and also films the whole thing on a movie camera. One scene involves him being fed a large green capsule containing poison, and even though everyone saw the whole thing, nobody can agree on exactly what happened or who committed the murder. Gideon Fell has to use the supposedly objective film footage to prove what really happened. Or take The Problem of the Wire Cage, also published in 1939, in which the locked room is not a room but a tennis court. An obnoxious young man who was taking advantage of a wealthy young woman is found dead in the centre of a clay court, and the soft clay only shows one set of footprints going towards the body – the victim’s own. And yet he did not die by his own hand. How was it done? That’s the mystery.

But Carr’s take on the impossible crime didn’t come out of nowhere — his work was only possible because of everything you’ve already heard about in this episode.

Jim: Carr did so much inside of the subgenre with how he mixed together all of the pre-existing ingredients. Everything brought in by Poe and everything brought in by Doyle, everything brought in by your Gothic writers, by LeFanu, everything brought in by Chesterton,  this incredible melting pot of these wildly diverse ingredients and turned out these hugely creative plots and these hugely creative characters that are also incredibly well-written 

Caroline: Carr slyly acknowledged his debt to his predecessors in plain sight too, in the character of Dr Gideon Fell, who shares some of the Father Brown creator’s physical attributes and opinions — “Fell is G. K. Chesterton, of course,” Carr once said.


Another writer who was active towards the golden age and contributed a lot to the impossible crime canon was Christianna Brand. She’s perhaps more often remembered by the public at large today for writing the Nurse Matilda series, the basis for the Nanny McPhee films. She didn’t write nearly as many novels as John Dickson Carr, but some of the ones from the 1940s featuring Inspector Cockrill are truly inspired, Jim feels.

Jim: Green For Danger, Tour de Force, Death of Jezebel. Have these magnificent casts. These magnificent uses of psychology inside of the crime. I think Brand did a lot of stuff that she doesn’t necessarily get credit for, for instance, people talk about The French Powder Mystery by Ellery Queen as being this incredible story where the killer’s identity is revealed in the final line. Now I mean that’s true. Anybody paying attention can deduce who the killer is before the final line of The French Powder Mystery. But if you just want to wait and be told, then you can be. You can just be told. In the 1940s, Brand wrote a book called Suddenly At His Residence, also known as The Crooked Wreath, where the fine line reveals not just who the killer is, but how they worked the particular crimes. Well it’s, it’s this very pithy, wonderful moment where you realise everything has been kind of funnelling down and it’s it’s arguably a far more accomplished. Distillation of what Queen was doing in The French Powder Mystery

Caroline: And of course, we should touch on the Queens of Crime in relation to this subgenre. Actually the only one of those four famous authors to try out the impossible crime in any serious way was Agatha Christie, who did it twice in full length novels: Murder in Mesopotamia in 1936 and Hercule Poirot’s Christmas in 1938. In the former, a woman is found bludgeoned to death in a locked room within a courtyard that nobody can have entered or exited unobserved. In the latter, a wealthy old man is heard fighting with an assailant in his locked room and when his children break down the door, he’s dead in a big pool of blood and there’s no way anyone else can have got in to fight with him or to cut his throat. I think both of these are among her top rank of plots, but they’re good more because of her skill with character and dialogue than because the plots really push the boundary of the impossible crime in any meaningful way. But then there is one that she wrote which is really like nothing else at all.

Jim: The one exception to that being somewhat debated as to whether it qualifies as an impossible crime, of course, being and then there were none, which is just one of the finest novels written ever, regardless of genre. I would personally consider that an impossible crime. I included that in a list of my fifteen favourite and impossible crime novels. Some people debate whether that technically follows is an impossible crime. But if you’ve got 10 people on an island on all 10 of them have been murdered and there’s no opportunity for the murderer to escape, then. That strikes me as an impossible crime. 

Caroline: Alongside English language impossible crime practitioners like Christie, Brand and Carr, there are lots of other authors that often get overlooked in these discussions because their work hasn’t, until now, been very widely translated.

Jim: Also, let’s not forget, there was a certain amount of stuff done in the impossible crime during the Golden Age that wasn’t done in English. There are French authors such as Noel Vindry or Marcel Lanteaume or Pierre Boileau or just before the Golden Age, of course, Gaston Leroux with The Mystery of the Yellow Room, that those of us who are not intelligent enough to speak a second language are only just starting to learn about because there are new translations of these coming out. There’s the Honkaku stuff that was written in Japan in the in the 1930s and 40s, Seishi Yokomizo and things like that that are just being published. I mean, there are some incredibly inventive examples of this that can be found, not necessarily Anglocentrically that people who have had an understanding and a knowledge of these cultures have known about for the intervening 80 or 90 years. And some of us are only starting to learn about now and starting to get very excited about it as well. 


Caroline: The creativity and innovation behind some of the best golden age impossible crime stories burned fiercely during the 1920s and 1930s, but what happened to this subgenre when the classic murder mystery began to fall out of favour after the Second World War?

Jim: There’s no doubt that there was a period where the detective novel certainly started to lose its lustre and start to fall from favour. And I think, as I said earlier, the impossible crime and the detection concept was so key, they grew up together and so they fell out of fashion together. 

Caroline: John Dickson Carr was still publishing Gideon Fell novels into the 1960s, but even he had slowed down and was experimenting with historical melodrama alongside it. And new crime writers who were emerging at that time weren’t interested in reshaping what had by now become the pretty tired old trope of the locked room mystery. P.D. James, who published her first novel in 1962, was writing police procedurals, as was Ruth Rendell, who debuted in 1964.

Mainstream crime fiction, then, had turned away from the playful puzzles and the fair play obsession of the golden age, but there were other kinds of genre fiction that could be stretched to incorporate elements of the impossible crime, for those who still felt it had some mileage. But constructing these intricate plots was definitely a niche activity.

Jim: There were a couple of examples written into the 50s and 60s and 70s, a lot of them by authors, interestingly, who then went on to write just pure science fiction. So you’d get someone like John Sladek, who wrote a couple of absolutely brilliant impossible crime novels, Invisible Green and Black Aura. I believe it was Sladek who said one could go hungry from just writing detective novels because they simply weren’t popular at the time. Or someone like Mack Reynolds, who wrote a novel, The Case of the Little Green Men, I believe it was called, in which a series of supposedly impossible events happened, the only explanation of which appears to be aliens. So someone wakes up and finds that wall burned by a laser beam. Someone is found having been dropped from a great height, as if having been thrown off a flying saucer. 

Caroline: The great American science fiction writer Isaac Asimov also wrote some straight detective fiction about a group of mystery solvers called the Black Widowers. But in 1968 he published a short story collection called Asimov’s Mysteries that are crime stories with paranormal or sci-fi backgrounds, and in the introduction he reflected on the compatability between the two genres.

Jim: And he said in the introduction, people seemed to see science fiction and detective fiction as entirely non sympathetic genres, because you could just say, I want to find out who the killer is, well, I’m going to point my Liar-Tron 500 at everybody and ask them if they killed them. And then my Liar-Tron 500 will tell them, will tell me sorry if if they’re lying. And he said, that’s actually fine, you can do that. But then why not write a universe which contains a Liar-Tron 500 and come up with a reason why that then can’t be used and fall back on scientific principles for your detection.


Caroline: In a way, the impossible crime story came full circle, because by the end of the twentieth century, writers were doing something quite similar to their counterparts at the end of the nineteenth century. They were experimenting at the edges of plausible science and technology to create scenarios that would baffle and delight readers. And of course, as real world science advances, some of these stories date rather badly.

Of course, people are still trying to write impossible crime stories and locked room mysteries, but things like forensic science and advanced surveillance don’t make it very easy to create plausible yet impenetrable plots. As a result, Jim says, a lot of the locked room mysteries published today aren’t very good.

Jim: There’s a lot of so-and-so was stabbed outside of the room and then fell into the room and locked the door after them to protect them. There’s a lot of oh, yeah, they just happened to consume a poison an hour before and then they fell down dead at a time that it made a pair as if it was impulse. Was a lot of sort of very hoary late Edwardian, early Victorian stuff, which is a shame. That’s some good work being done. Adam Roberts wrote a very interesting, again, science fiction crossover novel called The Real Town Murders, where a body, a dead body turns up in a car manufacturing plant where no human actually has any access. It’s a fascinating idea.

Caroline: That, I think, is a stroke of genius — what better setting for a contemporary locked room mystery than a full automated factory where no humans ever go?

Jim: There are some authors doing some interesting work with it these days, but they are definitely in the minority. Someone like James Scott Byrnside has self published two extremely good impossible crime novels Goodnight, Irene. And The Opening Night Murders, both of which have a real understanding and a real desire to go back to what the classic era detective fiction novel was, was trying to achieve. 

Caroline: It’s no surprise, then, that most of the authors still trying to write locked room mysteries today are writing historical fiction or speculative fiction.

Jim: But I find it interesting that they do tend to exist either in broadly speaking, either in people setting books back in the eighteen hundreds or early nineteen hundreds or people setting books in the 22 hundreds of the future.

Caroline: Part of what made the golden age the perfect period to incubate brilliant impossible crimes, it turns out, was that there was just enough of a popular understanding of science to make these plots plausible, but not so much that the writers had no wriggle room. Add to that the sense of interactivity and fun that the fixation on fair play provided, and you had the perfect conditions for this subgenre to flourish.


But even though we’re now almost a century on from that, I do think you can still detect traces of the human obsession with apparently unsolvable puzzles that made the impossible crime such a force in crime fiction. It’s there in the 1990s British TV show Jonathan Creek, or the mass popularity of escape room experiences.

We might not have someone like John Dickson Carr writing today, but we’re still desperate to work out whodunnit behind the locked door.


This episode of Shedunnit was written and narrated by me, Caroline Crampton, and edited by Euan MacAleece. You can find show notes and links to Jim Noy’s writing about impossible crimes at shedunnitshow.com/lockedroom, where there will also be further reading suggestions on the topics we covered today. I provide transcripts for every episode of the podcast too: find them at shedunnitshow.com/transcripts

If you become a paying supporter of the podcast, you get early access to every episode of the podcast with no advertising, as well as the chance to join the excellent Shedunnit Book Club community. For instance, if you’d like to hear a much longer version of my discussion with Jim and get lots more detail about impossible crimes and locked rooms, book club members will be able to do that via their monthly bonus episode. You can join now at shedunnitbookclub.com/join.

I’ll be back on 30 September with another episode.

Sorry, comments are closed for this post.