Rules for gaming mysteries?

[Commander Roj]

This blog http://preacherbyday.blogspot.com/ details a mini campaign using Cluedo as a tool to stitch together games of Pulp Alley.

[Charles92027]

I have the same objective. I'm an avid reader of cozy mysteries, and I've been looking for a game with less emphasis on gunplay and fisticuffs but simulates questioning witnesses and searching for clues. I wound up writing my own rules wherein, in addition to shooting and punching, characters can engage in a "battle of wits" with NPCs, to gain information and determine the location of clues. I didn't eliminate shooting and punching, because violence is part of what makes the bad guys bad.

Tokens for Clues (objectives, plot points, etc...) are spread through out the board based on the scenario's description. Their identity is unknown to the player until they pass a challenge using their "Savvy" ability. Then the payer draws a card, from the clue deck, that reveals what the clue is.
However, some cards are left out of the deck at the beginning and only shuffled in based on events in the game. e.g. If you find the metal detector, then shuffle the card for the gold bar into the deck. Or, question the bystander (by successfully beating him in a battle of wits), and shuffle in the card for an object he might have seen, like a gun hidden in a sewer grate. In one case I made a part of the board inaccessible until a map was found.

In one particular scenario, there are three phony bombs, and one real one, and several clues throughout the board that include the plans to the bank, a tool kit and the detonator.
There is a shuffled deck with three red card and one black one, that represent the bombs,
And another deck that represents the other clues, less a card for the detonator.
If you have not found the detonator, the bomb goes off in six turns.
Each bomb token requires two successes with your savvy ability to draw a card, and you have to keep trying until you find the real one.
If you are able to catch one of the bad guys, without catching a bullet, you can question him and shuffle the detonator into the clue deck.
If you find the bank plans, you can eliminate the red cards from the bomb deck.
If you find the tool kit, the bomb can be defused with three successes, but if you haven't found it, you need six.
If you have found the detonator, the bomb will not go off at the end of turn six, however, if you fail at defusing it, it will still go off.

The keys to the system are the battle of wits as a non-violent way to extract information from witnesses, informants and suspects, and making the clues unknown to the player, with some of them only being available until some other event occurs.
I have some written rules, but they're pretty rough and incomplete. DM me if you want a copy.

In the end it really comes down to scenario design more than an actual rule set.

[Pattus Magnus]

Thanks all, for the additional suggestions, there are some great ideas there! I’ll have to take a closer look at Strange Aeons, I actually have that book (the 2nd edition version), but missed the non-combat parts.

I really like the ideas by Charles92027 about having some parts of the scenario in stages so that a success is needed to ‘unlock’ access to other clues. That game mechanic fits well with the mystery genre and gives potential reasons for the players to re-interview npcs or return to specific locations.

[Pijlie]

Following this with interest. 

[Easy E]

Might I suggest a concept where as you gain "clues" it allows you to access more dice for "investigation checks".  Then the more successes you get, the more "clues" you earn.  Therefore, as you gain more clues the easier it is to uncover the chain of events that lead to the conclusion.

How do you imagine structuring the victory conditions.

[Charles92027]

The trick is to keep information away from the players. Without a Dungeon Master that's difficult, particularly in a solo game like so many of us are playing these days

In my games, I put the clues out there as unknown markers and only reveal them based on the character's progression through the game. In essence the solution is known, but the path to get there varies. Using a Cluedo style mechanic, the solution is unknown, and the clues reveal what is not the solution, until only one possible solution remains.

I could see combining both techniques in the same scenario:

A clue deck containing items that help the characters progress through the game (e.g. key that opens a door to a locked room), and a suspect deck that could contain not only who dunnit, but also other things like the where and how. But, for the sake of this example,. let's say it only contains who.
Shuffle the suspect deck, pull a card without looking and sequester it.
The clue deck and suspect deck are shuffled together into a Play deck. Some cards may be left out according to the scenario, but the reserve clue and suspect decks remain separate. Those cards are added into the Play deck based on events that occur: e.g. the card representing the uranium pellet is added after the characters find the Geiger counter, or interrogating the butler reveals that he saw something suspicious - shuffle a suspect card into the Play deck.

Each clue token is unknown and completing a challenge allows the character to reveal a card from the Play deck. The card could be a clue or a suspect. Once you know all the suspects except one, you know the solution.

Determining the solution could, of course trigger an event, e.g. Colonel Mustard says, "You'll never take me alive", and decides to shoot his way out.

I think, for a good mystery, rules matter less than the scenario design.
Any of these ideas could be applied to Pulp Alley, Astounding Tales, or whatever, as long as there is a mechanic for solving problems without resorting to violence.