On 50 Locked Room Solutions of Our Own

Late last year, I saw the Van Dine and Ronald Knox commandments for writing mystery fiction and, with no credentials, qualifications, published history or authority in the genre, decided to take a stab at proposing my own set of rules in On A Decalogue of Our Own. With even less in the way of credibility behind me, just two months before that I made a post to the Golden Age Detection Facebook group where I challenge the locked room taxonomies of Locked Room King John Dickson Carr and the late, but still highly-regarded, widely-read and deeply-esteemed locked room mystery historian Robert Adey. Where Carr suggested eight, and then Adey twenty, I set out with the conceit of naming no less than fifty unique prospective solutions to the three major schools of impossible crime.

I can safely say, and would like to say early, that I absolutely do not believe that my knowledge of the impossible problem comes close to Robert Adey’s, nor do I think that I ever will have the opportunity to even humor the idea of rivaling him. Robert Adey was clearly no less than a hundred times as dedicated to the craft as anyone I’ve known. This “challenge” of his taxonomy was more in good-humor than anything. The Adey taxonomy was broad but inexhaustive, likely for the purpose of just capturing the quintessential 20 solutions; it was efficient for the right reasons. I wanted to take the idea to its (absurd) logical extreme and try my hand at a more exhaustive list of the conceivable possibilities, whether or not they’re frequent or whether or not there’s even a single novel out there to employ them. Rather than Adey’s task of efficiently, economically and academically conveying a clear idea about the genre, this is more like On A Decalogue of Our Own where I claim no authority and simply wanted to engage in a fun thinking/creativity exercise. For purposes of discussing the genre in its historical sense, I will always defer to Adey’s taxonomy before my own.

Below is a direct 1:1 copy-paste of the post as it appeared in the Facebook group, with changes to the taxonomy made to reflect some very helpful feedback from Scott Ratner. These changes include removing one of the original Adey 20, and consolidating a few groups of similar solutions into more broad but inclusive language. Furthermore, a solution proposed by Jack Hamm is incorporated.


When Dr. Fell, as the voice of John Dickson Carr, gave a lecture on the nature of the locked room problem in The Hollow Man, he theorized that the locked room mystery had only 8 basic solution types separated between rooms that are and are not hermetically sealed. Lectures by fictional detectives along a similar line appeared in Anthony Boucher’s Nine Times Nine and Clayton Rawson’s Death from a Top Hat, but analysis of the genre didn’t reach its opus until the release of Locked Room Murders. Locked Room Murders a (thoroughly informative) bibliography on over 2000 locked room mysteries and their solutions wherein the author and late disciple of the locked room mystery Robert Adey provides a consolidated list of 20 solutions to the impossible problem of escaping from a perfectly sealed room.
In my infinite hubris, I decided to take the genre by the horns and top Adey’s own list with my own contribution of no less than 50 locked room mystery solutions, not only expanding upon the possibilities with the traditionally sealed room, but also exploring solutions unique to the “footprints in the sand” locked room and “guarded room” problems. The solutions are suitably categorized


Included here are solutions which are applicable to at least two of the three locked room solutions dealt with. Traditional “fully sealed” rooms are marked with an “A”, guarded rooms “B” and snowprint locked rooms a “C”.

1: An accident or a series of accidents within the room led to the victim’s death. (ABC)
2: The victim committed suicide; he or a third person may later go on to stage it as a homicide. (ABC)
3: A secret passageway exists that permits entrance into and out of the room. (AB)
4: Victim accomplice. The victim didn’t commit suicide, but instead aided his killer, unwitting or otherwise. After he was wounded or otherwise prepared to die, the victim would create the impossible scenario. (ABC)
5: Some mechanical device or trap was set-up before the room was sealed which would kill the victim. (ABC)
6: The killer utilized imprecise and indirect methods that impact the whole or a large portion of the room through doors and windows, i.e. mass electrocution, oxygen vacuum, incredible extremes of temperature, poisonous gas etc. (AB) (Snowprint mysteries usually rely on the victim being murdered in close quarters, making this not viable as a means to establish the impossible scenario. Furthermore, while it can also be used in guarded rooms, it is not discrete and would likely notify the “guards” as well, but is still partially viable)
7: The victim was murdered before the locked room was created, but falsely made to look alive later. (ABC)
8: The victim was murdered after the locked room was opened, but falsely made to look dead earlier. (ABC)
9: The killer hid in the room and evaded discovery during initial searches of the crime scene. (ABC)
10: The killer murdered the victim from outside of the room by shooting, stabbing or launching the weapon into the room, or otherwise directly targeting them from outside; the murder was made to appear as if it happened from inside of the room. (ABC)
11: An animal which is capable of things a human is not committed the crime and escaped the room, or otherwise acted as an accomplice to the crime. The room is only considered “locked” because it is impossible for a human to escape. (ABC)
12: An acrobatic maneuver was used to escape the room in a way impossible for the typical human. (ABC)
13: When a locked room isn’t observed by the sleuth before re-entrance, the belief that a locked room mystery occurs is a lie imparted by key witnesses, the culprit and/or the victim, including but not limited to faked death. In other words, the case is a lie with varying degrees of fictionality. (ABC)
14: The room was destroyed or otherwise deconstructed from the inside and reconstructed from the outside. (AB)
15: The victim was convinced, coerced or forced to partially exit the room or take an unusual position so that an attack that would otherwise be/seem impossible could be made. (ABC)
16: The room is not stationary. The movement of the room permitted the killer to leave the room. (AB)
17: The room is not mundane. Some strange quality of the room was used to kill the victim. In other words, the room is the murder weapon. (ABC)
18: An identical room is employed to confuse witnesses. (AB)
19: The killer is in the room, and in plain sight; however, the killer is falsely exonerated due to a fundamental misunderstanding of the crime including, but not limited to, the gender/appearance of the killer, the motive of the criminal, or the killer victimizing themselves so that they are incapacitated or otherwise appear incapable of committing the murder, (ABC)
20: The room was constructed around the victim after the murder. (may demand a more metaphorical definition of “room”). (ABC)


These are solutions which are only applicable to the traditional problem of a room locked perfectly room the inside.
21: Key is turned from other side of the door, by pliers or similar, picking of the lock, or other means of gimmicking a door, including the “credit card trick”.
22: The door was locked from the outside; the key was replaced inside of the room after the room is opened, so that upon discovery it looked as if the door was locked from within.
23: The door was locked from the outside; the key was replaced inside of the room before the room is opened, so that upon discovery it looked as if the door was locked from within.
24: The culprit, who is the only person who can lock the door from the outside, is provided with a false alibi at the time of the murder.
25: The killer pretended to break an already broken lock or chain to make an unsealed room appear sealed. Elsewise, the “fake keyturn” trick.
26: The room was “untraditionally locked” in a way that can be either performed from outside of the room without a key, including powerful adhesives or moving furniture; witnesses are misled to believe the door was locked.
27: The key inside the room, or another object, is believed to be the key to the room; it is not.
28: The murder happened while the door was open, but in such a way where the death resulted in the door being shut.


Represented here are solutions that only apply to locked rooms that are created by the room being watched and guarded by witnesses.
29: The killer is exonerated by not having something the killer is assumed to have (i.e., stolen goods in a locked room robbery, or an impossible-to-dispose-of weapon); the item is disposed of from inside of the room, cleverly smuggled, or disguised.
30: A distraction allows the killer to leave unnoticed.
31: Witnesses don’t take note of the killer due to classist divides and/or psychological principles of incongruity (the bellboy would certainly enter a hotel room, so the bellboy is not noticed).
32: The killer leaves by a route observed solely by accomplices.
33: The killer leaves because their route is temporarily obscured from sight.
34: The killer leaves by an opaque container that is removed from the room.
35: The killer is one of the people guarding the room, left unattended due to trust or status.
36: Disguises, gimmicked voices and other impersonation stunts allow the killer to escape the room.
37: The killer used sleight of hand to commit the murder in front of people without being seen.
38: The killer used a tool in order to commit the murder in front of people without being seen (i.e. fake hand).
39: Mirrors were employed to confuse witnesses as to the location of the killer, victim, or the room itself.


Included below are solutions which are exclusively applicable to the problem of “the victim is killed in close quarters in snow/sand/dust/powder but there’s no footprints”. For purposes of brevity, the snow/sand/dust/powder will herein be referred to as “the substance” (roughly equivalent to “the room” in universal solutions).
40: The killer wore their victim’s shoes.
41: The killer had some means of crossing the substance without leaving marks.
42: Aerial movement; the killer used an elevated surface or machine to move above the substance.
43: The killer walked backwards so that it looked like the footprints were caused only when discovering the body.
44: The killer did leave marks, but hid them until after discovery of the body so that it looked like they were created then.
45: The victim was murdered elsewhere and was slung, launched, swung, dropped or thrown into the substance without otherwise marking it.
46: The killer used cleverly crafted shoes or stilts to disguise their footprints as other markings (like animal prints).
47: The killer was at the crime scene before the substance was placed down and left after the crime using a route that doesn’t disturb the substance and would be inaccessible without doing so if the killer hadn’t already been present.
48: The killer erased their footprints.
49: The victim was murdered remotely, made to appear as if it happened in close proximity. The wound that appears to prove the crime happened up close was inflicted posthumously, after the body is discovered. Elsewise, a fatal projectile (such as an arrow) was removed upon discovery of the body to make the wound appear direct (like a stabbing), or a remote gunshot was doctored to appear as if shot from close-quarters, perhaps through false ballistic burns, or other means of gimmicking/forging the wound. (remarkably similar in 10, distinct in that 10 deals with the nature/location of the weapon itself, whereas 49 deals in the nature of the fatal wound. Furthermore, 10 assumes the presence of the weapon, whereas 49 typically assumes the disappearance of the weapon)
50: The killer walked over the same footprints so much that their footprints would be falsely identified as the victim’s; especially reliable if the victim is seen stumbling over themselves.

3 thoughts on “On 50 Locked Room Solutions of Our Own

  1. scottkratner May 9, 2021 / 1:59 am

    A great list, and certainly approaching exhaustiveness than the others. But does it include a place for the explanation provided for the past impossibilities cited in Till Death Do Us Part?

    Liked by 1 person

  2. scottkratner May 9, 2021 / 2:00 am

    I meant “certainly more closely approaching exhaustiveness”

    Liked by 1 person

    • scottkratner May 9, 2021 / 2:51 am

      That is, would the limits of universal solution #13 extend this far?

      Liked by 1 person

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