In Episode 2x02 - The Hounds of Baskerville our Mr. Holmes is - once again - bored and wants a case:

Sherlock: I NEED A CASE! [...] What am I saying? This is brilliant. Phone Lestrade, tell him there's an escaped rabbit.

John: Are you serious?

Sherlock: It's this, or Cluedo.

John: Uh, no. We are never playing that again!

Sherlock: Why not?

John: Because it's not actually possible for the victim to have done it, Sherlock, that's why!

Sherlock: But it was the only possible solution...

John: It's not in the rules!

Sherlock: Then the rules are wrong!

Having never played the table top game (presumably that is what they are referring to) myself, I am unsure if that is a valid (and known) criticism of the game's rules (Google doesn't seem to think so: "Cluedo rules wrong" basically leads to quotes from the episode or are sites telling you that most people play the game wrong because they misunderstand the rules afaict) or if it is merely a throwaway gag from the writers?


4 Answers 4


The victim in Cluedo is always Dr Black. [S]He is not a player & has no player card, so their card can never be in the 'whodunnit' envelope. Therefore, they can never have committed suicide, by the game's definition.

By Sherlock's rules, if he has decided the only conclusion is that it was suicide, then by his definition, the game rules must be wrong.

I'd call this more a plot example of Sherlock's irascible personality than a true claim that he found a solution which is not possible - after all, once you have eliminated the impossible, whatever remains, however improbable, must be the truth ;)

  • 5
    You should point out the fallacy of "once you have eliminated the impossible, whatever remains, however improbable, must be the truth". Sure, it's a famous Sherlock Holmes quote, but it ironically points out how flawed Holmes (and probably Sir Arthur Conan Doyle's) thinking is. How can a mere human (even one as supposedly brilliant as Holmes) think of every single conceivable situation and evaluate whether they're possible or not? And what if the solution is possible but inconceivable until revealed? Basically, it's impossible to know if you've eliminated the impossible.
    – CJ Dennis
    Jun 12, 2022 at 0:39
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    I think you're taking this all rather too seriously. Sherlock's 'inspirational quote' is just a re-cast of Occam's Razor but with more emphasis on the 'possible'. It's a part of Holmes' character that if the world doesn't conform to his viewpoint, then it's the world that must be wrong.
    – Tetsujin
    Jun 12, 2022 at 8:38
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    Here in The USA, the game is called Clue, and the victimis is Mr. Boddy. Jun 12, 2022 at 18:29
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    How many people are aware how deeply flawed Sherlock Holmes is? He's a fascinating and entertaining character, but he's not nearly as smart as his reputation suggests. Occam's Razor is usually expressed as "the simplest solution is usually correct", but it's actually "entities should not be multiplied beyond necessity" which means "the solution with the fewest assumptions is to be preferred". The simplest solution could be "magical pixies did it", but it assumes the existence of pixies, it assumes they're magical, and that they have the motivation to do the thing, all of which are unwarranted.
    – CJ Dennis
    Jun 14, 2022 at 2:01
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    @CJDennis: not really a fallacy. If you are certain that a hypothesis is false, you can rule it out. Mathematicians and scientists do it on a daily basis. The problem is that it is, in many situations, extremely difficult to list all possible hypotheses. The irony is that Sherlock often doesn't follow this method. For example, when Watson and Sherlock meet for the first time, there could be a million scenarios explaining John's leg and the state of his cellphone.
    – Taladris
    Jun 14, 2022 at 4:00

It is just a simple joke about Sherlock's stubborn refusal to consider that he might have missed the point, or to see things in anyone's terms but his own. You don't need to know the rules of Cluedo to get the joke ("Then the rules are wrong!" is enough), but I feel it adds a layer.

Watson is right: Sherlock's theory is simply comically impossible in the rules of Cluedo, and Cluedo is not "broken" - but it does have a problem with the kind of human errors that Sherlock hates to allow for.

Cluedo's gameplay hinges on players accurately responding to queries about the secret cards they are holding. If a player says they don't have a card which they have but absent-mindedly overlooked, it can break the game: other players may build logically-sound deductions on this that can cost them the game because they're built on a false premise.

This is a throwaway gag, but as someone who grew up playing quite a lot of Cluedo, it painted a very vivid picture for me:

  • Sherlock had (maybe reluctantly) agreed to play a game with Watson (and probably others). Once he started playing, he got far too immersed in the murder-mystery premise
  • He built elaborate deductions on every move another player did, as a good Cluedo player does. Unfortunately, someone at some point made a human error, so his logically-sound deductions took him to an impossible place.
  • He obviously would not ever consider that his logic could have been at fault
  • Normally at this point, the keen-eyed player would say "Hang on, that's not possible because [list of six observations from the last 10 rounds] means you can't have X card" then someone would say "But I do have X card. Oh, I must have made a mistake 10 rounds ago" and it gets very awkward, the game falls apart, and it possibly ends in an argument.
  • However, Sherlock being Sherlock, it appears he got so absorbed in the murder-mystery premise of the game, he lost track that this was just a fun social activity between fallable humans, where possibilities are limited to which cards actually exist and "a player messed up" is a valid possibility.
  • In keeping with "Once you have ruled out the impossible, whatever is left, nomatter how improbable, must be the truth", he constructed an elaborate narrative that made sense within the imaginary fictional universe of the game, but not in the real-life scenario of some not-quite friends awkwardly trying to play a board game with a high-functioning sociopath.
  • Watson tried (and failed) to reason with him and save the game; but also had to be careful to avoid exposing whichever player had made the human error, because you can just imagine how Sherlock would have treated them.

It's a throwaway joke that conjures an amusing image of a long-suffering Watson trying to sustain a normal social event around Sherlock's peculiarities.

I'm not 100% sure it actually works though... Human errors in Cluedo tend to result in false certainty of an option. I can't see any way someone in a Cluedo game could logically rule out all options of a type, as this line implies.

Like a lot of details in Sherlock, it's best enjoyed if you think about it a little, but not too much.

  • 3
    False eliminations could happen if the players are not following the rules correctly, and saying "I have card X" instead of showing card X to the player who asked (which is what the rules say you're supposed to do). Then you could falsely claim to have a card. For example, let's say that Sherlock has (correctly) deduced that Scarlet did it, and asks "Scarlet, in the Hall, with the Lead Pipe," in order to try and rule out one of the weapon or the room, and some other player (incorrectly) says "I have Scarlet." Then Sherlock will conclude that nobody could have done it.
    – Kevin
    Jun 12, 2022 at 0:42
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    We've had cases where two people asked for the same card and both times it went all the way around with no cards shown. Thus; we know somebody goofed.
    – Joshua
    Jun 12, 2022 at 3:44
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    @supercat - one and the same thing.
    – Tetsujin
    Jun 12, 2022 at 17:36
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    @supercat - everyone seems to be getting really, really pedantic about this question. I'm really not sure why. If you want a clearer explanation, see my answer, not my comments. This answer fails to allow for that one single fact… Dr Black is not a player. Dr Black is the game's sole victim, time after time.
    – Tetsujin
    Jun 12, 2022 at 17:49
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    @SethR any writer who doesn't expect at least stack exchange level of analysis should not be writing for any iteration of Sherlock Holmes. Jun 14, 2022 at 2:49

From what we know about the character, I suspect Sherlock might not have bothered trying to follow the rules in the first place, or indeed to even learn what they were.

While most of us might think of Clue(do) as an entertaining game of deduction, for Sherlock, playing it the way it's intended to be played would likely be incredibly dull. So, rather than play along - going turn-by-turn, asking who has which cards and so on - it's quite plausible Sherlock would try to approach the case as he would any other: by observing the suspects, crime scene, "police report", etc... Basically, all the "flavor" that's largely meant to be ignored.

I like to imagine a group of folks gathered around the board, their initial enthusiasm fading fast, as over Watson's futile attempts to intervene Sherlock delivers an extended, rapid-fire monologue:

... Naturally the murder weapon couldn't have been the dagger. Even the police aren't so incompetent as to miss traces of blood that ...

... couldn't have tied the knot, which was clearly made in a hurry by someone right-handed, whereas from his tie it is obvious that Mr. Green is, in fact, left-handed ...

... in that short time Miss Scarlett couldn't have possibly made it to the library undetected, all the way from the lounge where she had been chatting up Professor Plum (rather pointless, as it's apparent any interest he may have in women is purely academic) ...

... you're asking yourself: "Then who set the dining table"? Wrong question. What you should be asking is why. Well ...

... Therefore, we must conclude that this was no murder at all, and that the perpetrator was, in fact, Dr. Black himself!

This does bring up one question: if Sherlock has already "cracked the case", why would he propose playing it again? But I'd say it's more than possible he paid so little attention to the rules ("unnecessary information" not worth storing) that, in his mind, the game could well deliver a new set of facts each time.


Cluedo (Clue in the US) was developed during WWII by a musician who was trying to pass the time during air raids. It was developed as a Murder Mystery Game in the vein of Agatha Christie novels. As such, it's impossible for the person who died (Dr. Black in the UK, Mr. Boddy in the US) to have committed suicide. To make this obvious to the players, the victim has no playable cards. I.E., Mr. Boddy can not have killed Mr. Boddy in the Study with a rope.

The gag allows for the conclusion that in an earlier Cluedo game, Sherlock made an error in that he somehow eliminated everyone, including the murderer, from being a potential suspect. Hence his statement that it was the only possible solution.

The UK rules explicitly state, "This evening Samuel Black was found murdered in his mansion!" The presumption by Sherlock's statement is; if it was a suicide, there is no murder and therefore the rules are wrong.

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