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The Toolkit: Mystery, Part Two

Previously on the Toolkit, we made a basic mystery system that should easily fit into most roleplaying systems, and D&D 5e in particular. This week I want to show how this system could work in a short, self-contained adventure that you can slot into your campaign. So how do you write a mystery adventure?

The Crime

Establish the crime or mystery your players are investigating early on, taking into account the kind of tone you want the adventure to exude. A light-hearted caper probably shouldn’t start with a ditch filled with severed limbs (unless it’s based on Fargo, in which case it probably should) and likewise, a tense, grim thriller shouldn’t start with a thief stealing everyone’s left sock, or a serial flasher.

Don’t feel limited to giving your players murder investigations, thefts can be equally interesting without needing to be gory. If your players are fairly mercenary in their outlook, having a highly valuable item as a stake will gain their attention. Kidnappings are a great starting point too, providing a lot of tension if the party is under a time limit to find the culprit and the victim before it’s too late.

There is one golden rule to follow when it comes to plotting crimes to kick off an adventure; no matter how much drama and tension it might create, if a crime is so heinous it makes your players uncomfortable at the table, you need to tone it down or rewrite it. Obviously your mileage may vary, but it’s something to be aware of.

Whatever the crime is, you should ensure the PCs strongly feel the need to resolve it. Perhaps the victim was a contact or close friend of the party, or the victim’s family are offering something incredibly valuable to the person who solves the case. If you’re planning to use an adventure to kick off a campaign, you could even add motivation into the character’s background through their bonds and flaws, like this example from my Super-Secret Project (shhh).

One Day from Retirement

You’ve served the law (as a watchman, a constable or some similar position) for most of your life, and it’s almost time to retire. They’re making you a cake and everything. You might be planning on spending more time with your spouse or your grandchildren, maybe you’re building a house, looking forward to a long fishing trip, or perhaps you’re ready to take up adventuring in your twilight years. Whatever you have planned for your retirement, it won’t stop you from throwing yourself in front of a citizen in danger or from taking on the toughest cases. You’ve still got 24 hours left on the clock. Gain an inspiration point when you get injured protecting a citizen from imminent harm, or take on a difficult case.

For my example adventure I want to feature a dinner party and a murder, for nostalgia. As this is a slot-in adventure, the motivation for the PCs needs to be something obvious and that will grab the most attention, but you could always tweak it to suit your PCs interests better.

Upon arriving at Dragonstone Manor to deliver a package to the wealthy landowner Silas Dragonstone, the party discover that he has been murdered. Apparently butchered in a spectacularly bloody fashion at a dinner party, he was found dead in the foyer between the main and dessert courses. Miles, Silas’ eldest son, has offered a king’s ransom to anyone who can find the guilty party amongst the guests, and bring his father’s killer to justice.

The Perp

It might sound like basic common sense – because it is – but establishing a clear guilty party early on when writing your adventure makes everything that follows flow much more easily. Don’t try to leave the details open to improvisation or last-minute changes. As tempting it is to try and throw off your players, inevitably it leads to confusion and an unsatisfying climax to the adventure.

A key part of establishing the guilty party is determining their means, motive and opportunity, that they had the ability to commit the crime (whether that means they have those particular skills, access to a certain kind of weapon, etc), the inclination to do so (and more importantly, why they want to commit the crime), and the opportunity to do so (being in the right place at the right time).

Silas Dragonstone was killed by Marion Forte, an officer of the Emperor’s Dragoons from a rival family who had attended the dinner party with Silas’ youngest son, Artis, who is also her lieutenant. Marion butchered Silas as he left the dining room to answer the call of nature, and is waiting until the situation calms down to abscond with her lover, Artis.

Plotting a Path

Have you been to The Angry GM’s fancy new website yet? If you haven’t, you really should. Pretty much everything on that guy’s website is RPG gold, but there’s one section in his latest adventure-building article series that summed up everything you need to know about structuring an adventure:

“The truth of the matter is that every adventure is a dungeon adventure. An adventure’s structure just shows how the scenes and encounters are interconnected. But you can map ANY adventure as a dungeon.” – Every Adventure’s A Dungeon, The Angry GM

There are some demonstrative diagrams and examples within the article as well as some interesting insights into transitory elements; it is well worth a read. My main take-away was that the adventure and the motivations of the player characters in that adventure serve as a sort of framing device, so that even when you run a game in a sandbox setting, players are likely to follow a path based on the cues that you provide for them.

In other words, if you clearly signpost where your clues lead to, you can direct the flow of the adventure, or at least keep your players from wandering off the map into unplanned territory. Treat each new scene as an encounter, with clues serving as transitions from one scene to the next. If the one clue the PCs find is a beret with the badge of a local regiment, you can bet it’s likely their next stop will be the local garrison.

Angry’s method — as seen in Every Adventure’s a Dungeon —  for structuring adventures works perfectly here, so we’re going to borrow it. Draw a box; put the Crime at one corner, and the Perp at the other. See all that space between the two? That’s the adventure.


Now draw a path between the two, add some corners and at least two dead ends. This can be as winding or as simple as you need it to be.


Finally, put a text box at any point where the path turns a corner or comes to a dead end. I neatened up my path just to make the boxes fit more nicely in the limited space I had. Protip: Make sure you draw a bigger box.


There you go, now we have a rough adventure structure, or a dungeon map. Each dead end represents the end of an avenue of investigation, but as you’ll see these don’t represent failures on the PC’s parts, but a means of tightening the net.

The Cluedo Elimination

Unless you’ve been living in a hole for the last forty years, you’ve presumably heard of Cluedo (or Clue to our American friends) and are aware of the basic premise of the game. For my hole-dwelling friends, Cluedo is a portmanteau of Clue and Ludo, where the players travel across the board attempting to piece together – by process of elimination – the particulars of a murder at a dinner party.

Maybe you’re more familiar with Guess Who? No, not the Bernie Mac/Ashton Kutcher remake of Guess Who’s Coming To Dinner, though that probably has some interesting roleplay applications in there somewhere. I’m talking about the board game with two boards filled with pictures of odd-looking people with different sets of defining characteristics. The players ask each other questions about an individual such as “Do they have ginger hair” and flip down characters on their own board until they have only one remaining.


A good mystery adventure needs to give your players the chance to use their heads, and a great way to do this is to let them work through the process of elimination. Depending on scale, this could be an entire city, the attendants of a dinner party, or just a handful of people. Make sure your clues eventually narrow the field of possible suspects, not just lead them in a merry goose-chase.

Go back to the path we plotted. As I said, every dead end should represent the end of an avenue of investigation, but it should also add another piece of the puzzle. In the example path, there are three dead ends, so three opportunities for the player characters to narrow down the list of suspects. Now you can do this next part without the aid of a diagram, but sometimes it’s just easier to have a record of your thought process.

Draw a table something like the one below, with a column for potential suspects, plus one column per dead end on your path. In these dead end columns, think of a broad category that your perp fits into, and use it for the heading.


Then fill in the blanks, think up a few suspects that fill two of these categories, and a couple more that fit one category. As the PCs discover new clues about the identity of the perp, they can cross names off their suspect list. The more dead ends you include in the path, the more categories you can include.


Once you’ve got your list of suspects and some categories to narrow them down with, you can fill in some of the blanks on your mystery path. Think of a clue that would – without too much ambiguity – link to one of these categories, for instance, if I wanted a clue to link to Officer of the Emperor’s Dragoons, I might include an officer’s “pip” or epaulette badge with markings – to those in the know, via backgrounds and mystery points – peculiar to the Dragoons. That won’t single out a definite suspect, but it points to the category without any room for misinterpretation.


You see the rest of those blank text boxes? If this adventure was a dungeon, they would be the rooms where we’d experience encounters or something interesting (no-one wants to spend half an hour talking about walking down a featureless thirty foot corridor). These are our scenes, the interesting ones that provide the meat for our adventure.

Scene First

Just because we’ve plotted a dungeon-like path for our adventure doesn’t mean you’re limited to scenes based on moving from one location to the next in a linear fashion. These scenes could be individual locations, the same location viewed with the perspective of new information from the previous clue, or even dialogue with NPCs, with new routes of questioning or interviewees available thanks to additional clues.

A single-location or single-NPC adventure can be an interesting prospect — if you don’t believe a story told in a single location with a limited cast can be interesting, go watch Carnage — and a great payoff for the players can be to have a clue make them readjust their thinking and return to a previous location to discover a clue hidden in plain sight. That said, go with what feels good for you.

Think of a handful of interesting scenes, dialogue or encounters, and arrange them in an order that makes sense to you.


Now you just need think up some clues to link them together.

The Clues

You know why so many roleplaying adventures fall flat when it comes to story progression based on skill checks, or the GM has to flounder for a while whilst they have the players try any number of skills until they finally succeed on a roll? That’s because eventually someone is going to fail a crucial skill role. So don’t make that a deciding factor of your game.

As I discussed in my last mystery article, there are better systems for running mystery campaigns, but let’s presume that you want a slot-in mystery adventure for your D&D, Pathfinder or other generic fantasy or sci-fi roleplaying game, here’s the simplified version of the Gumshoe-inspired rule I worked out (examples and a bit more reasoning behind the rule are in a previous Toolkit):

When the player characters first enter a mystery scene, give each player one Mystery Point. These work like limited Plot Points that the players can spend when they encounter a Key Clue to declare a story detail, describing how they can decipher the Key Clue’s meaning using their past experience and knowledge. Once all Mystery Points have been spent, deal them out again, until the mystery has been solved.

As @brometheus said in last week’s Stories of the Fifth Age, it is essential that you pace the clues and make sure you don’t give the party anything early into the adventure that points straight to the perp. Link the clues to the scenes, rather than to the perp. Try to make sure there are clues that appeal to a wide variety of backgrounds, otherwise you run the risk of having your players struggle to come up with ways to solve them. This article by Stephen D. Rogers is intended for murder mystery novels, but most of the guidelines there should help to guide your thinking.


As an example, here is the first clue, and how I would link it to both the mystery point system and the next scene.

Despite the meticulously-polished marble floor in the foyer, you can see that streaks of some kind of waxy-feeling substance, smelling faintly of orange and reminiscent of stately homes and libraries, occasionally mar the surface. Presumably this waxy substance was tracked in after the floor was polished. Spending a mystery point and pairing it with an appropriate background (such as a Noble or Sage, but let the players experiment, the roleplay is more important than the rule) will reveal: This wax is most likely a high-quality wood wax, of the sort used to burnish expensive parquet floors. The only room close to the foyer with a wooden floor is the trophy room, which the players could spot without the need for a roll.

You should now have the tools to make a basic mystery adventure, go out and experiment with the adventure structure, interesting crimes and perps, and how to enable your players to eliminate innocent suspects. Next week, I should be wrapping up the mystery segment of the Toolkit with red herrings, magic and special tech, and finishing up our murder mystery into something you can slot into your D&D 5e campaign.

Like this article? Have any suggestions or requests for tools you’d like to see in the future? Let me know here at the Mad Adventurers Society or via Twitter @jay_jaydraper.


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  1. The Toolkit: Walking the Earth | The Mad Adventurers Society on Thursday, August 27, 2015 at 5:10 am

    […] you can recall the short series I wrote on mystery adventures, I talked a little about signposting (based on The Angry GM’s article “Every Adventure’s a Dungeon”). The principle here remains […]

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