Aligning GUMSHOE General and Investigative skills

Don’t get me wrong I love GUMSHOE, really I do. I think the philosophy behind it is sound and works really well in action. It makes investigation play flow well and once the players understand their characters the investigative abilities fade in the background and are replaced by questions and answers.

I have played it in its Trail of Cthulhu and Night Black Agents incarnation, I have read the base rules, and most of the other settings using it. In short GUMSHOE is now my go to system for pretty much any game. That being said, I have now more sessions under my belt and I found some problems with it. Nothing that can’t be fixed or that completely changes the system. Some of those problems are even fixed in later implementations of the system.

Here are the problems I have seen at my gaming table and my proposed fixes. To make sure my solutions do not bring worse side effects, I have placed upon myself a base set of requirements, Unit Tests, that must always be kept in mind.

  • Keep the system using 6 sided dice
  • Stay simple, it can be explained in < 15 minutes
  • Changes should be minimal

The fact that a system like GUMSHOE can accept hacks of this type speaks to its solid design.

Problem #1 – Overlap

Large amount of abilities (investigative or general), something with a large overlap between them. Later incarnations (Timewatch, The Esoterrorists 2nd Ed ), have fixed this by reducing the number of abilities. So I won’t spend lots of time here as this is already taken care of, and the solution is so simple it makes monkey brain hurt.

Problem #2 – The Leak

That one will be tricky to explain. I call it the “I always win until I don’t anymore.” problem. It only occurs with general abilities. This is due to the use of the pool system and the pure 50% chance of success on most actions. In my experience it is frequent that a player will use 2-3 points for every general skill use.

Using 2 points gives the player a success rate of 83%, using 3 points gives us guaranteed success on standard difficulty 4. Varying the difficulty rating between 3-8 makes the problem more apparent as players are often unwilling to go below a certain success ratio threshold. So they spend enough points to almost guarantee success until they have no points left leaving them (the players) in a confused state of what their characters can do.

This is called a leak in computer science, where your resources are slowly drained. Adding more build points to a highly used skill only pushes the problem to later, but it remains there.

Problem #3 – Scale

The scale difference between the skill sets, while I understand that Investigative and General abilities are not used the same way in game (sometimes they are, some general abilities can be used in lieu of an investigative one).

Build points for character advancement can be used to increase proficiency in General or Investigative Abilities, but since both sets do not work on the same scale this feels clunky.

Problem #4 – Binary Results

The current GUMSHOE system treats any result equal or higher than the target as a success, anything else is a failure. The lack of varying degrees of success is one of the main reason why problem #3 happens, players abhor failure. Compounded by the lack of critical success or failure it leaves the players with only two choices, win/lose.

Problem #5 – Too many guests

Health, Stability and others (Network, Cover, Aberrance) as general abilities. These should be renamed to attributes as they are used for a completely different reason. I would not change their current scaling as I believe that a greater range offers the players more to play with here.

Constructive Criticism

If these are not problems that you see, then you are good to go with the base system. If like me you see them happen sometime at the game table, then I propose an alternative skill system. Is this system overkill, maybe, I don’t know. I believe the solution to be really simple and in-line with the current GUMSHOE system, there might be issues with the proposal, but until it is play tested we won’t know for sure.

An alternative general skill system.

Note : You never roll for clues – This does NOT change.

The proposed solution reworks the skill ratings to a unified range of 0-4 for both the Investigative and General skill sets. By making both sets follow the same range it makes it easier to give meaning to the rating a character possess. This change does not apply to Health/Stability, only for abilities.

On character generation the number of Investigative Build Points remains the same. For General Abilities the SRD recommends using 60 build points, readjusting this on the fly is harder. But taking 8 as a high rating in a single skill to be replaced by 4, the adjusted number should be 30 build points.

* Every time a skill description contains the following “8 or more points in X grants you 1 free point of the investigative ability Y.”; the new system will assume a rating of 4 instead of 8.

Unified Ratings Table

Rating Description
0 Untrained – Most skill roll can be attempted. Skill marked with an * require at least a base knowledge
1 Indicates a formal training in this domain, this represents basic knowledge on the subject matter such as introduction university courses or training.
2 Indicates a good understanding of the subject matter and/or actual field experience. A character with this skill level can be considered to have a masters degree on the subject.
3 Indicates an excellent understanding of the subject matter, you can actually teach others about it, a doctorate level or extensive field training.
4 Indicates constant use of that skill, you are probably the head of your department and are invited to speak on the subject matter.

* Higher ratings indicate super human capabilities or extremely large creatures.


Once character creation is completed using these new ratings we need to change the way Simple Tests are handled. Since every other roll in GUMSHOE is based on the Simple Test mechanic we won’t repeat everything here. Simple test are made using 2 six sided dice, points from the general skill the character is testing on can be added to the roll. The result is then compared to the following table.

Result In Short Description
2 Fumble You failed miserably, it should not have happened, but it did. Figure out how. Think of something bad.
3-6 Failed You failed, it happens, you’ll get them next time.
7-9 Partial Success You succeeded, but it was harder than expected. Think of a consequence.
10-11 Success You succeeded, as expected. You are that damn good.
12+ Critical Magic, you made it look so easy that you probably have fans. You spent 1 less point than expected. If you spent 4 points it only cost 3.

*Apocalypse World to the rescue



      Attributes are a new definition for an existing type of abilities. In the standard GUMSHOE system, health and others are considered abilities but work differently. No game system changes are required for them, but placing them in a different group makes it easier to explain them.

Health, Stability and Aberrance should not be changed at all, this also means that the damage system is not changed and remains as is. Special attributes that are used to create skill like pools, like cover or network, would pick one additional rule. The created skill pool must be in the [0-4] range.

In-game Refresh

     Whenever the rules mentions that a character should get an in-game refresh we recommend a refresh of 2 points.


     A rating of 4 in athletic now gives a -1 modifier to the roll result when trying to hit the character. Hit threshold modifiers should now be considered negative numbers to be applied to the resulting roll.

Desired Location Modifier toHit Threshold
Large carried object (rocket launcher, laptop computer, backpack) -1
Torso, windshield -1
Chest (if attacker is facing target) -2
Gut, specific window, tail rotor -2
Head or limb -2
Hand or foot, joint, tire -3
Heart, throat, mouth, or face -3
Weapon or other hand-held object -3
Eye, headlight -4
Chest (if target faces away from attacker) -4                                         


Sample Creatures *source GUMSHOE SRD

Aggressive Herbivore, Sauropod-Sized

Abilities: Athletics 12, Scuffling 12

Health 36

Scuffling Weapons/Damage: trample +8

Hit Threshold: +4

Armor: 1

Alertness Modifier: +4

Stealth Modifier: +4


Apex Predator, Lion-Sized

Abilities: Athletics 6, Scuffling 4

Health: 8

Scuffling Weapons/Damage: bite +1

Hit Threshold: 0

Armor: 0

Alertness Modifier: -1

Stealth Modifier: -1


     GUMSHOE offers cherries to characters that have high level ratings, these cherries are special abilities that give cool looking capabilities to the characters. Cherries become available to characters for abilities of rating 4. Once a skill is maxed out, a player can buy cherries at the cost of 1 build point per cherry. This allows for a large set of possible cherries and differentiation between characters. Rewriting cherries as moves would be a good way to make the cherries an integral part of the system.

*[In some games, you may wish to trick out general abilities with the following fillip:]

Almost every General ability has a cherry, a feature that kicks in when the character has 4 rating points or more in it. Agents can always use that special benefit, even if their pool in that ability has dropped to 0.

Example Cherry: Crackers’ Crypto

Prereq :  Digital Intrusion rating at 4

Cost : 1 build point to buy.

Description : Get 1 free rating point in the Investigative ability Cryptography. You can also encrypt your team’s electronic communications against all but government-level (NSA, GCHQ, MID, DGSE, GRU, Unit 8200, etc.) cracking.

[From Night’s Black Agents]


Final Notes

This probably needs lots of play testing and does not cover all cases, but after thinking about it, I am pretty sure it solves my issues with the base system. This is an idea I would like to see expended on. Our gaming group will probably start using this in our next game, if you have any suggestions, comments, or criticism please leave a comment.



Apocalypse World –


Casefile GUMSHOE –

WhineSHOE: Rethinking GUMSHOE –

3 thoughts on “Aligning GUMSHOE General and Investigative skills

  1. Simon Rogers says:

    Hi, I can’t see how you handle varying difficulties using this system.

  2. monsieuryan says:

    I was thinking of basic penalties [0, -4] added to the result, so a climbing a rotten ladder would be a -1 to your athletic test, while jumping across rocks floating on molten lava could be -3.

  3. jukujin says:

    #4 is discussed in Trail of Cthulhu somewhat. I can’t remember exactly where, but it talks about failure not being interesting. The example given (iirc) is that if you make a player roll for climbing a fence, but not climbing the fence could stop the story, don’t make straight failure an option. Essentially, the PC will get over the fence, but they may take a consequence for it, e.g. hurting their leg.

    This is somewhat a contrived example, but the idea is “failing forward” (I can’t remember if that phrase is used in the book or not, but that’s how I’ve heard it described somewhere).

    I don’t know that this is precisely what you’re discussing here, but it’s how I’ve come to deal with the problem. Players realize that, as a GM, you’re not going to strand them because of a bad roll, so it also addresses point #4’s impact on point #3.

    In short, while the success or failure of the roll is binary, the result of success or failure on the story isn’t, so it stops being a problem.

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