How To GM Mysteries
Posted by: Jendor -- January 14, 2015


By Istrian

General Tips


A mystery can usually be narrowed down to the 5Ws and one 1H: Who, Where, When, Why, What, How. A mystery can also have multiple instances of one of these.

For example, Where could lead to multiple locations, each being related to the mystery in a limited way. At the same time, each of the Ws can be related to some other minor mysteries, thus creating a large web of mystery.

Since players draw conclusions from what they have found, they are likely to mix things up and try to do things to confirm their hypotheses. That's why some improvisation will be required.

Is Failure Acceptable?

That's an important decision and do not withhold this answer from players.
Failure can mean many things:
  1. The PCs take too long in their investigation and the culprit gets away
  2. The PCs consider they have done enough
  3. The PCs do not wish to take further risk and are ready to close the case
  4. The group simply runs out of clues
If failure is not acceptable, it will be necessary to have contingencies planned for critical stuff to fall into the hands of the players (but they must, of course, pay a high price for it).

Know Events, Improvise Clues

You won't know ahead of time how players will proceed when they try to unravel a mystery. And it is impossible to predict the result of rolls. As such, I find it best to not make lists of clues to be found.

Instead, I write out vague events (Bill and Bob had a fight in the dining room in the morning) and improvise the actual clues depending on how the players act (the butler was hidden nearby and saw the fight, blood stains on the carpet, either of them sporting a few wounds, and so on).

Give Clue Overload

I find it best to give a lot more clues than to try to hold to a few important ones, and then let the PCs sort it out by themselves.

This gives you several advantages: players always have leads to follow even when they lead nowhere, and it creates a greater feeling of immersion into an actual mystery.


I love them. Witness NPCs are best way I've found for delivering loads and loads of leads upon the PCs, most of them usually unrelated or complete rubbish.

NPCs see things, but they may not understand them, or remember them right. They might just make up things to fill in gaps in what they believe they saw to appear credible, or to make themselves interesting.

Some will even lie outright for their own reasons while not being bad people themselves.

Let Them Try

PCs will do unforeseen things. They go to unexpected locations or talk to undefined NPCs. However, with the knowledge of the events that transpired to lead to the mystery - and some subtle fact manipulation - you can create a link between whatever the PCs are doing and the truth. For example, be ready to give more importance to some minor NPC you neglected if the PCs think he can help.

Random Generation

Don't forget to help yourself by having some NPC generators. After all, how likely are they to talk precisely to the NPC you created rather than to some random passerby who seems to be related to something?


Tell your players, "This is a mystery, there is a solution, I know how it begins, I know how it could end, but I have no idea how you will get there. So I will be improvising a lot, but it's not because it's improvised that it's unrelated. And if something looks completely illogical, ask me OOC, and I'll tell you if I made a mistake or if it's illogical IC".

Mystery As Main Plot

When the PCs' goal is to unravel a mystery and whatever they do with the solution does not really matter, then in my opinion, failure (partial or complete) must be an option.

Hold A Briefing

In this case, I believe the most important part is the Briefing. This may take any shape or form, but it is simply the hook that contains a significant amount of information, with only half of it relevant, and less than 10% as actual truth.

One thing that must be made clear to the players is they are only required to investigate everything in the briefing, or as much as they can. The minimum I put in the briefing is a clear reference to at least 2 NPCs, 2 locations, and 2 mysterious events (for players who like to talk, those who like to search or infiltrate, and those who want to browse libraries for anything similar).

The rest of the investigation is up to the players. They might even come up with stuff that wasn't in the briefing or planned at all. The best thing to do is to roll with it (perhaps secretly roll a die to see if it has any link with the mystery). Obviously, there must be no critical clues, only stuff that leads either nowhere or to more stuff.

When to end the mystery is not up to the GM. It is up to the players to say when they are done. There could be an actual objective (find the missing people, arrest the murderer) and even deadlines. Make these as clear as possible.

One campaign I'm currently running has PCs investigating paranormal events. Their only goal, as stated by their superiors, is to find the truth, or as much truth as possible, while keeping a low profile. Usually they start with a full briefing containing press articles, reports, maps, and other stuff that has a load of information, on many different topics, not all of them related. Usually it mentions an event, a location, and the names of a few people involved (journalists, police, criminals). It usually also contains some information that may be useless, like background checks, unexplained events, seemingly-related events in other places many years before, etc.

Next to that, I have written down the actual events, and how they are related to one another. What each NPC is aware of, what they try to do every day, their general goals, etc. With this I can improvise scenes on the fly depending on where the PCs go and what they do.

And I don't have a grand finale planned. The PCs can decide at any time they have enough information and write a report to their superiors, possibly recommending some course of action. In the end they are not judged on what they do, but on what they found and deduced. They can also call upon allies and contacts to do the action and dangerous stuff while they do their investigation.

Mystery As An Obstacle

In this type of mystery, the PCs need to find some information to move forward. What matters is they get enough information to think they can do something.

The GM's job is to drop as many relevant but incomplete clues as possible until the PCs have found what they think they wanted to find. Fortunately, it's simple to do, as anything the PCs do can drop a clue as a side-effect. For example, having an enemy they killed drop the clue as their dying breath, or finding a diary or letters while searching for loot to sell (which very often happens), an NPC randomly mentioning something while talking about something else, etc.

The breadth of each clue must be limited: it only points to one of the 5Ws and 1H, and possibly not reliably.
In a story arc I am currently running, the PCs want to either destroy a certain organization or bring it under their superiors' control. In the beginning, they received a sparse briefing containing 4 locations and are running through them to find information on what the organization is doing, and its strengths and weaknesses.

Recently, they have run through a "dungeon" that was one of the organization's local HQs. They found out the location was nearly vacant after its occupation by a demon. The players were uncertain whether the demon was summoned by the organization or if it was unrelated. They simply went in and kept looting through - I mean, looking through - rooms to collect clues while fending off endless waves of enemies. Eventually, they decided to retreat after finding a lot of stuff.

Fortunately, none of them could read the languages of some of the letters they found (and didn't take the time to read through the larger clues while fighting), so it let me give them the clues I needed to make them feel they didn't need to return to the dungeon (they didn't want to anyway). All they found, other than the large pile of loot, were clues about how the organization was smuggling construction materials to some unknown place for unknown goals. And the name of someone who looks like he might be behind it all (never underestimate the power of ominous names).

Mystery As Filler

It may seem weird, but sometimes the mystery does not need to be resolved and is a side-story that might have a positive outcome if solved, but the PCs can just dump it if they don't want to work on it.

Usually for these, since I am never sure if the players will take the bait, I tend to improvise everything using a simple technique. Whenever the PCs talk to someone new or are about to find something significant (by virtue of rolling high on their "Find Stuff" roll), I roll a d10 and refer to this table (this one is geared towards murder mysteries but can easily be adapted):
  1. The clue points directly to the murderer...unfortunately it is stolen or destroyed right before delivering its secrets all the while making it clear it was very important. For example, a key witness dying in front of the PCs.
  2. The clue is a fabrication planted by someone to divert suspicion from themselves.
  3. The clue unambiguously points to a credible truth. However it is unrelated and using it will harm the PCs.
  4. The clue looks convincing and related but leads to an unrelated fact that a cunning PC might be able to exploit later on.
  5. The clue does not look credible, but does point to the truth. For example, the ramblings of a madman.
  6. No clue.
  7. The clue is ambiguous, but slightly narrows down the list of suspects. For example, indications on hair or eye color.
  8. The clue could greatly help the PCs move forward, however it would require some legwork that might not be easy. For example, retrieving samples of blood or fingerprints, or a map to a dungeon where the truth could be hidden, or making someone talk when they don't want to.
  9. The clue is precise enough to narrow down the list of suspects to only a few.
  10. The clue is one of the keys to the mystery. For example, when the PCs are actually talking to the culprit or to a willing accomplice.
Anytime a roll is made, the GM needs to tie it in with what was previously done, for consistency.

It is important to keep these mysteries short to avoid mixing up facts. For example, one could end up with three murderers.

One time I used this method was when the PCs were on a ship pursuing the leader of an assassin group. The main investigator (who was not a PC) was poisoned and decided to act dead while asking the PCs to gather as much as possible to avoid another murder attempt.

The PCs already knew the assassins wear necklaces as distinctive signs, so one of the things they started to look for was people's necks.

(Rolling a 3) They noticed one NPC wearing a necklace under their shirt (therefore not seeing the important part), and the NPC was reluctant to reveal what it was. Unfortunately, the NPC was not an assassin but someone sent by a nobleman one of the PCs wanted to work for, to check on the PCs' abilities. Unfortunately again, the PCs were brash and went to the ship's captain to force the NPC to reveal their identity.

So they did, and it harmed the PC in the long run.
Meanwhile, they managed to find (10) a vial that contained the poison with which the investigator was poisoned, and (8) talked to the brother of the murderer who didn't know about the murderer part but while talking to the PCs realized the murderer was acting suspiciously.

Unfortunately, this led to his death when he confronted his brother in secret, but helped the PCs take down the actual murderer.

Hope this helps others with their mysteries.
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