I've always wanted to run a game like Call of Cthulhu, Monster of the Week, or Silent Legions, but I've never really had the patience for that kind of game. Complex backstories, intricate plots, and overwritten adventures made it difficult for me to wrap my head around actually running a game like that. It is easy to run a survival horror scenario; all you need is something trying to kill the player characters, an isolated area, and a couple possible means of escape/survival.
But with an investigative game, there is a lot more you need to consider. For one thing, you need to give the player characters some form of motivation to actually go look in the haunted house, or hunt down the werewolf. Its all well and good to have a group of survivors in the zombie apocalypse try and survive the oncoming horde by hiding in an abandoned hospital, nobody would question that, but why would someone want to go into the scary haunted house where 7 people have been found dead in the past 10 years? And why, when the going gets tough, would they not just leave?
I think the trick is, that an investigative scenario should be divided into 3 stages: Hook, Research, and Confrontation.
The Hook is possibly the most difficult part to get right, since the entire rest of the adventure relies on it. Much like Descartes searching for a single truth to base his entire philosophy on, the rest of the game relies on you finding a good reason for the party to be there. Fortunately, this isn't all your burden to bear, and the players have to help as well.
Something I've always felt was missing from Player's Handbooks of all kinds is a section entitled "Make A Character Who Actually Wants To Go Adventuring", where it explains that being smart and playing things safe is not the reason why you're sitting down to roll dice, and that if you want anything to get done you have to take risks and make someone who has actual reasons to do stupid bullshit. If its your first session for a horror game like Silent Legions; ask your characters to make characters who want to go hunting for monsters and find eldritch secrets, not just some innocent bystanders who get thrown into harm's way.
Anyway, with the player facing side of the Hook out of the way, next comes the GM's part. You should give more than one good reason for the party to look into the mystery. Come up with things beyond just, "its a local legend and there have been strange noises at night". If you can, try to relate the hook to a player character's backstory and personality, to make it more plausible for them to look into the matter.
Research is the second stage, and this is the part that might require a bit of improvisation on the GM's part. In this stage, the players want to find out as much as they can about the mystery without just rushing head on into danger. Heck, they might not even know where the danger is yet. When they start asking questions and wanting to go into libraries to find old books and things, you have to have a list of things they could possibly find out on hand somewhere, along with clues. Keep in mind that you're probably not a genius mystery writer, and your players aren't Sherlock Holmes, so not every clue is going to stand out to them. In order to combat this, give them a LOT of information, but not enough to know exactly whats going on.
For example, lets say you're running a game where a group of vampires are holed up in an abandoned cabin, and have been killing livestock and the local homeless population around town. Your list of information and leads should be something like:
- Someone's dog was found dead in their backyard a few nights ago. (If the players look in further, they will discover it had no blood left in its body).
- Old Joe, an elderly vagrant who panhandles outside of the local grocery market, isn't there anymore, and nobody knows where he went. (He was last seen heading to his makeshift camp by the woods. If players investigate, his body can be found, deathly pale and drained of blood, a zipgun in his right hand which failed to fire).
- There have been lights and odd cries coming from the woods at night. (The only possible source of light in the woods is an old cabin, long abandoned, and the cries sound like human laughter.)
- Farmer Hanson's cows have been acting spooked, and several have died mysteriously in the night. (Also with those strange puncture wounds and no blood).
- There have been a string of odd grave robberies. (All of those whose graves have been "robbed" were, in life, members of a strange blood cult, and the graves seem to have been dug out of rather than into.)
The above information should be enough (along with a couple NPCs written up), to run the research portion. Each piece of information not in parentheses could just be given to the player characters, and what is in parentheses could be found out through some investigation.
After Research, the party should have a general idea of what might be going on, and begin the Confrontation phase, going to the spot where the weird stuff is originating, and trying to stop it. For this phase, all you really need is a map of the area, and what kind of stuff/people/creatures are there. This is much like a dungeon crawl, but should be more grounded in reality, with realistic layout of buildings, logical rooms, and a decent sense of cohesion.
And there you have it! Hopefully, with a little practice I'll be able to write up some fun investigations, and maybe put them up here on this blog. I hope you've enjoyed this little rant!