While your game may not be set up specifically to be an investigative game, at some point in time you are very likely going to have some sort of mystery in your game. Mysteries are, sadly, very messy things, and not much will set your players down wrong paths and frustration faster than one that isn't set up right. So, how do you do one right? Honestly, I'm not 100% sure, but I have found some pointers over the years, and will happily share what I've found helps me. Read on for more.
The Long Haul
First off, when you are putting a mystery into your game you need to understand that you are in for the long haul. Plotting a mystery takes more prep time than almost any other type of game. Actions scenes are cake by comparison, especially once you get the threat assessment for your system of choice down. What makes mysteries so much harder? Well, quite simply, you can't afford to have plot holes. Everything needs to make sense with a mystery, because any incongruity in the flow of events can completely derail everything. As such, be prepared to go back over what you've done again and again to find where the holes are and fix them. Trust me, it works out better this way.
Quite possibly the easiest way to set up a mystery is to work backwards. Don't start with the situation the players will find first, end there. Start with what actually happened. "Bob kills Joe with a hand gun." That's the end of the plot right there. Mystery solved, so now ask yourself the big questions. Why, Where, and How. Why did Bob kill Joe? Because Joe was sleeping with Bob's wife. Where? In the park down the road from his home. How? With a gun he borrowed from his friend Stacy. Keep asking yourself questions about this until you have the whole situation done. Once you know how everything happened you can finally go to the beginning. Why? So you can lay a path to the desired end that the players can follow.
Layout the Scene
So, you have the ending planned. That means you need to go to the most important part of the whole shebang. The scene of the crime. Why is this the most important part of the mystery? Because it is the launching point for everything that comes after. This is where the story begins, and if it can't get things going then your mystery is likely doomed to be a weird fizzly flop. So, try to make it memorable. Remember your details you set up earlier, you need to give at least one clue that will bring the players one step closer to that conclusion. More is preferable, but at least the one to start things off.
In mystery stories and shows you almost always have the red herring. Sometimes it is a false red herring, but then it still serves the same job. Basically, a path or conclusion that seems real but actually isn't. In a TT game you want to be careful with these. Make sure there is some clear evidence to be found to kill off a red herring if it is looked into, and not rely on the players looking at gathered evidence in a certain way. Honestly, in most situations the players will come up with so many crazy theories on their own, that you'll be too busy coming up with reasons theories may not work to really throw your own loops out there. This is actually a good thing, because once you bring doubt on information coming directly from you, it can be hard to get full trust back. Just one of those weird things about the human psyche in my experience.
So be careful with your false trails, use them if you want, but know they are dangerous. I can't stress enough how important it is to have a place where the dead end clearly ends and points the characters back firmly towards the info you gave them that leads to the right place. Be sure to help sheer out the useless stuff that is picked up as well.
Wrapping It Up
Wrapping it all up, just be careful with how you run things, and be open to weird interpretations from your players. It is very possible that your players will come up with things, and ways to jump to the next part of the mystery, that you never thought of. Be open to rolling with it, and don't be too proud to switch things up a bit if a player theory is going to be even more fun than what you had planned. Aside from that, be clear with your information, and make sure that there is a definite chain of clues that lead the players to the end. There can be other things out there as well to help, or cloud, but there should be a straight and clearly defined chain.
Have fun with it though. Anyone have other tips to share on this?