The (Classic Doyle) Whodunnit Formula

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Without a doubt, the whodunnit is the most popular type of mystery there is in modern culture, and if you read or watch a mystery story today, it’s probably a whodunnit. CSI? Whodunnit. The Mentalist? Whodunnit. Criminal Minds? Whodunnit. Detective Conan/Case Closed? Whodunnit. Murdoch Mysteries/Artful Detective? Whodunnit.  

People love figuring out whodunnit!

Which is why it might come as a shock to you that most Sherlock Holmes stories, the paragon of mystery crime solving, aren’t whodunnits. Doyle actually preferred howdunnits and whydunnits instead, at least based on the number of each he wrote.

Oh, the criminal is often unknown until later in the story, but the focus of the stories isn’t so much on who did it, but how or why it was done, and the criminal’s identity is often secondary to figuring that out. This is one of the things that may make reading Holmes a bit of an adjustment for modern readers, since Doyle seems to have found the simple question of who did it much less interesting to hang a story on than how or why it was done. Sometimes the criminals even turn themselves in “off camera” once their schemes are revealed because it just isn’t that important to the story.

However, he did write whodunnit stories from time to time for variety, and the formula he used isn’t much different from the others at heart…

Introduction (15% or less of the story, 900 words in a 6000 word short story)

  • The main detectives are introduced in an interesting way which shows off their personalities.
  • A new character with a problem (hereafter called the “innocent”) appears before them and the main detective character shows off their detective skills by guessing information about the Innocent.

The Situation (35%, 2100 words)

  • The Innocent tells the detective characters about their problem. The innocent tells them the details of what happened which lead them to coming to see (or calling for) the detectives.
  • A crime has been committed and there are two or three suspects who could have committed it. The mystery is built around figuring out which one of them did the crime.
  • The Innocent will tell the detectives their story, which will include all suspects (although they may be under fake names), the important details of the events they’ve experienced, and a few important clues (which they might not realize are clues and just think are details). The detective will catch these clues, but probably won’t put them together or mention this to the audience. The clues should be worked into the story in such a way that they don’t stand out as being clues and fit in with the rest of the Innocent’s story unless the audience pays very careful attention.

The Investigation (20%, 1200 words)

  • The detectives will take action to help the Innocent, usually by going out and gathering more clues or information.
  • If there’s not a lot of information, then we might follow the main detective and their partner as they talk to various people involved in the case. They may interview witnesses, examine crime scenes, or collect the stories of the people involved.
  • If there’s a lot of information to be gathered from various sources, the main detective and their partner may split up and then meet again later to compare notes. This is to speed up the process of telling the story by having one or both of them summarize the information they learned for each other and the audience.
  • Often the case will get stranger, or there will be a twist, near the end of this phase (but not always). The most common twist is the elimination of the “red herring” where the most likely suspect is proven to be innocent by dying or new evidence showing they’re innocent. (This is why there is usually three suspects – since one will be eliminated from the list at this point.)
  • At the end of this phase, the main detective (and the audience, maybe) will have the key information they need to solve the case and will often say that they know to their partner. (But not tell the audience what they’ve figured out.)

The Reveal (30%, 1800 words)

  • The main detective will now take steps to catch the guilty party.
  • The detective gathers the guilty people together and tells them what really happened, explaining how each of them is connected with the crime until they settle on the real criminal last. The real criminal reveals why they did it when confronted with the truth, answering any questions the audience might have like motives (usually hatred because of past events or greed).
  • With the crime laid out, the audience should be able to look back now and see clearly how everything fit together in a reasonable way. There should be no magic powers, acts of god, or huge co-incidences, and everything should make sense.
  • Usually, there is one last unanswered question, and in the final scene the detective’s partner or the Innocent asks it to the main detective, and the detective answers them in some interesting way. The final scene usually ends on either a final thought or (in later stories) on an amusing note to balance out any tragedy which the ending revealed with positive emotions.

The above formula can also be used for novels, but would require a bit of expansion and development to make it work. One of the advantages of whodunnits is their ability to be padded out as much as needed by simply spending more time exploring and learning about the backgrounds of the victims and suspects. Subplots about how the crime was done and motivations are also easily incorporated into a whodunnit story as needed.

Generally, the main clues that reveal a culprit in a whodunnit story are going to be verbal ones – they say the wrong thing while giving testimonies or answering questions. Occasionally, it might be something they are tricked into revealing by the detective, in which case it is often something simple and innocuous were it not connected with the current case. However, spoken mistake are rarely enough to convict a person of being the criminal, so there will need to be other physical evidence available to support it and finish the case.

Detective Conan Mystery Formula

Image result for detective conan

The following formula, found on Reddit and submitted by user TeraVonen, is a near perfect summary of the typical 2-part story pattern you find in the mystery anime and manga Detective Conan. Conan is the 4th best selling manga series of all time, and the anime has been on the air for over 20 years, and in that time a definitely formula to how the stories play out has developed. There is still a lot of variety within this formula, but it’s the basis of the majority of Conan episodes which aren’t directly linked to the overarching plot.


The typical murder case Detective Conan episode

Part 1 :

  • Conan goes with some of his usual companions somewhere for leisure.
  • Optional: Conan thinks about some plot progression elements he recently discovered. *
  • Conan’s group run into a group of people. One of them is being a douche to everyone else and then goes somewhere away from the others. Conan will listen a bit to the argument then move on with his day.
  • A scream. Conan and any detective he was with (Heiji, Sera, etc) will go running to the scene. It’s a murder. The person being a douche earlier got killed.
  • The police come to the scene.
  • Optional: The scene might appear as an accident/suicide initially, before the detective confirm it’s actually a murder.
  • Conan starts citing strange things to the police. [Things that Conan notes as being strange about the case or situation- Rob]
  • There are three suspects: The ones who argued with the victim earlier.
  • End of the episode.

Part 2 :

  • The suspects are searched and interrogated. At least one of them has a good motive for the crime.
  • The police discovers new elements related to the crime, but still not enough to determine the identity of the murderer.
  • Conan and the other detectives (if present) are close to the truth, then someone in Conan’s group will bring up a subject or say something unrelated that will make Conan or the other detectives realize how the crime was committed.
  • At this moment, the three suspects want to go home and urge the police to let them go, they will explain again their own versions of the events to show how the murderer wasn’t one of them.
  • This is when the case is resolved, either by one of the adult detectives, Sleeping Kogoro, or Conan himself. The method of murder is explained and the culprit identified. They will deny it, claiming no proof, this is when the detectives will use the “We will find your blood/fingerprints/DNA” card.
  • The culprit admits his crime. His motive is either to punish an unpunished crime, getting blackmailed, or to avenge someone else. [Also hatred and jealousy are common ones- Rob]
  • End of the case, Ending starts.
  • Conan and his group move on from the case usually going home after having their leisure time disrupted.
  • Optional: If there is any plot progression deductions from Conan, they will be shown here. *

[ *  = These refer to the overarching story of the manga, not the individual mystery which this is a summary of. -Rob]


The above formula is best understood by watching a few episodes of Detective Conan (aka Case Closed in English) which can be found on Netflix or (better, because they have more episodes) Crunchyroll. Or, of course, you can also read the manga at various places online. It’s a nifty little mystery story structure for short stories that has been proven to work time and again.

If you wanted to use it for another type of detective story that wasn’t broken into two parts, however, you would need to make a few modifications. The audience knows who Conan is, whereas another detective would have to be quickly introduced. Also, in a short story you probably don’t need to have the suspects explain themselves twice, because that’s just for people who missed/forgot the first half to catch up before the reveal.

Anyhow, this was a great summary of the Conan story formula, so I thought it was worth archiving for future writers. Enjoy

Rob