Cross-posted from a similar rpg.net thread, the context was people complaining that with investigative rpgs if you miss a roll to find a clue the game stalls so you have to fudge, which is a fuckwitted way to approach scenario design IMO, I've seen people saying in all seriousness that CoC can't be run as written for this reason which I know from personal experience is simply wrong:

Firstly, if you're running an investigative game, you are an idiot if you put in one clue that if not found stalls the game. That's just stupid, it's like running a dungeon and putting in a crevasse at one point that must be jumped or the game ends, it's asking for trouble.

You put in multiple clues, on the basis the PCs are likely to get some and not get others.

Secondly, you think about what a failed roll means. Does a failed Library Use roll mean you don't get the clue? Or does it maybe mean you get it but not all of it, so you're missing some useful information. Or you get it, but it takes longer than you wanted and now you're under time pressure. Or you find the book, but the library is closing and it's reference only, now you have to decide if it's worth stealing or not.

There are tons of easy ways to deal with this, I see people sometimes posting stuff like how you can't run CoC as written, which is bizarre given I've done just that for years and know many other people who've done the same.

Alternatively, clues can be in people, talk to them and find out what's going on, again failed rolls may have outcomes which are bad but not you get no clue.

And what happens if the PCs bizarrely fail every roll they make? The exact same thing as happens in any game in which the PCs fail every roll they make, they're fucked. It's vanishingly unlikely to occur in practice, but if I run a dungeon bash and the players fail every to hit roll the game is fucked, however in twenty plus years of play I've never yet seen that theoretical possibility come to pass.

People really overthink this, mystery rpgs are not that hard to run, I've done it tons of times. If someone finds that they are having to fudge the rules because otherwise the players can't progress, that isn't a rules problem, it's a GMing technique problem. No different from the difficulties I have running Supers games because I don't have good techniques for those.

Quote from: WarthurAs far as Cthulhu is concerned, not enough information can be fatal. Failed Library Use rolls might still let the PCs find out that a particular ritual site is sacred to the cult of Glaaki... but not that Glaaki himself is said to appear there to receive sacrifices, for example.

Exactly, pass and you learn that Glaaki personally manifests, fail and you find that it is a site sacred to him and that many have not returned from it, fumble and you learn that it used to be a site sacred to him but is now thought abandoned.

You find the site, but how prepared you are when you get there is another matter...