As a new player in a game of Mutant City Blues, it has struck me that the GM has a very large workload when prepping the investigation scenes if there is to be any real interaction with that scene for purposes of discovery by the players. In a group that really wants to have the rewards of personally shaping how an investigation plays out, preparation time for the GM is immense and does not end before the scene starts, it continues and expands as the players take their queries in unexpected directions, all of which demand satisfaction due to the level of expertise each character possesses as an investigator.

Obviously, a GM could simply narrate the scene and build up to skill spends and the transition to scenes where the players are expected to act with their newfound information, but that diminishes the time players can spend in that investigative capacity and forces them to focus on their deductive abilities.

What works to reduce the amount of preparation for the GM while providing opportunities for the players to explore and investigate a crime scene or mystery?

  • \$\begingroup\$ +1, wishing for +5. I don't have an answer, but this is an excellent question. \$\endgroup\$
    – Tynam
    Aug 27, 2012 at 10:50
  • \$\begingroup\$ +1, I am eagerly awaiting a good answer to this question too :) \$\endgroup\$
    – Cat
    Aug 27, 2012 at 12:10
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    \$\begingroup\$ An essential book for any game involving police work is What Cops Know by Connie Fletcher. \$\endgroup\$ Sep 4, 2012 at 14:29

3 Answers 3


Things that I have found that reduce the time in preparing for "Crime" scenes, and preparing scenes that last longer than "go in, find clue, walk out". These are taken from my own experience when running Call of Cthulhu

  • Mind Maps; for any mystery an overview of everything is essential. A simple mind map of how each NPC relates to another with a circle-line drawing is invaluable. How this reduces prep time is that before every investigation area the GM knows what and who this particular scene relates to and how it can uncover clues to the mystery.

  • The ability to adlib, this can't be stressed enough from my experience. You don't need to specify to the nth degree what a crime scene has, just what the important pieces are. If the players are investigating an old shack where the murderers diary is then that's all you need to know. Then let the players investigate it and lead you to where it is; give a simple description of the place they're exploring and then let them lead into the details. There's a old dusty fireplace. "Is there a grate?" Yes there is. "Is there something under the grate" Yes there is. Feed clues in as players explore, it's a lazier way.

  • Play to the players abilities. If one player likes dusting for fingerprints, roll with that; you should as a game pans out know what the players like to do, this means you can work mostly to their strengths (and their feeling of competency) rather than determining every possible way a clue can be discovered. Players like to feel that what they've spent their valuable XP on is actually useful rather than time and again finding that they never ever find fingerprints. Or vary it, no they don't find fingerprints, but they do find a lip print on a glass; same skill, different ideas. Just just throw in a few curveballs out of their experience as well to keep them on the edge.

  • As a player, you can massively help the GM know what sort of stuff you're looking for by discussing things all the time between yourselves, let ideas flow out verbally so the GM (especially at the end of a session) knows where you'll likely be heading next game. This means they potentially only have to plan one or two places ahead of where you're going, rather than the whole lot. The rest can be simple clues and places, NPCs and ideas.

  • Speaking of NPCs. These are a fantastic resource for padding out encounters and bringing them to life. They don't even need to be plot elements, feed in shreds of the plot through different NPCs who are near a location. At the old cinema? Well the tramp in the back alleyway heard a splintering sound. The policeman on the beat saw a light upstairs. The janitor noticed that the back door was unchained. These can all feed into conversations along with snippets of NPC persona (who they'll maybe never even see again) but this makes things more real. These NPCs don't need full statboxes, just a simple description and persona; you can use resources like the one sentence NPC generator or masks to roll out Quick npcs whenever you need a tramp, cop or dinner lady.

  • Watch/read and learn: CSI, Sherlock Holmes, Hercule Poirot, Columbo. Look and see what these sort of people notice, take in ideas from everywhere you can and mix-and-match them to what can be useful; as a GM trying to find something new to keep the players interested can be hard work, but if you've seen ideas before you can mix and match them between to create hybrid ideas that are entirely new, this way also you've got a lot of stuff waiting to be created. This saves you planning stuff and makes things more lazy, horah :)

  • Dead ends. You need some occasional red-herrings. These can be generically generated for any mystery you run. Murder plot? Make a few random NPCs who are potentially connected with extra motives to give you breathing space for main investigations. Put in some random interesting objects to keep the players wondering, keep them guessing and ad-lib off the junctions; steer them back with NPC hints if you need to, or just let them walk down the road until they find their brick wall and have to backtrack.

Hopefully this is the sort of thing you meant :)

  • \$\begingroup\$ Exactly what I meant~ \$\endgroup\$ Sep 4, 2012 at 16:01

Instead of making a list of clues, make a list of facts that lead to the other scenes of the investigation. Encourage your players to use their abilities in ways that logically get the facts along with other cool things that spends can get.


Can I just suggest GURPS:Mysteries as an answer to this question? It has like two chapters of advice on very similar things (mystery adventure design generally, not specific to Gumshoe/MCB). Not all of it is specifically geared to reducing prep required for PCs shaping the investigation, but some of it will help (there are tips on information management and avoiding railroading, etc.)

Sorry if this answer is too much of a 'go here to find the answer', but it really is a good resource for mystery GMs.

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    \$\begingroup\$ Is there any way you could condense/summarize some of the advise pertinent to this specific question? \$\endgroup\$
    – AceCalhoon
    Aug 28, 2012 at 19:52
  • \$\begingroup\$ I am not ignoring this answer, but I am looking less for 'how to build a mystery' than for 'how to efficiently prepare for the investigation scenes in Gumshoe, ' with a side order of how to do that to allow the greatest freedom for the players to investigate. \$\endgroup\$ Aug 31, 2012 at 4:31
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    \$\begingroup\$ This is pretty much an exact answer to the question. Unfortunately, it's both a bit long to summarize effectively here, and copyrighted, so copy/pasting the text is a no go. Still, if you want to know how to prepare for investigative scenes in GUMSHOE, this book will cut your prep time down by about 50%. \$\endgroup\$
    – Be Cn
    Sep 10, 2017 at 23:46

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