Information Grids for Mysteries & Investigations

Note: This post contains spoilers for the Mothership scenario Another Bug Hunt. 

I love running mystery and investigation scenarios. Designed well, they allow players to engage in open-ended problem solving, often putting together the clues in ways I could never have anticipated. I like using the node-based scenario design approach for planning and running these types of situations, but one thing I often struggle with at the table is remembering who knows what. 

I've got my NPC notes in front of me at the table, but oftentimes the players ask questions that I didn't anticipate. I'm also frequently inventing new NPCs on the fly as the players look for clues or information. That's all well and good, but sometimes when this happens I either give out clues and information too readily or overlook obvious information the character would have known. 

To help, I came up with this play aid to keep at the table: a simple grid showing NPCs on one axis and information on the other axis. That doesn't automatically mean an NPC will share all this information - the PCs have to ask, and in some cases, may need to bargain, negotiate, deceive, or threaten to get the information they want. I use a simple key on the grid to represent this:

x = the character knows nothing about this 

S = the character knows about this and is willing to share if asked

H = the character knows about this but wants to conceal the information

Any information that would be well known by any NPC involved doesn't get put on the grid. They will just share it with the PCs (assuming they are not hostile).

I'm currently running the Mothership adventure Another Bug Hunt. The second scenario in the book, Hive Mind, has the PCs investigating the Heron Terraforming Station and interacting with three different factions each led by a different NPC. I created an Information Grid to summarize who knows what, and what they're willing to share.

You could modify this to include false beliefs that NPCs have, if you want to include red herrings. You could also make a similar version for locations and location-based clues, particularly if you have a lot of locations to keep track of or don't have detailed location notes.

It's a simple tool, but it helped me keep track of who knows what, especially when multiple NPCs are included in the same scene or if I have to come up with a new NPC on the fly, I can easily slot them into one of the categories.