Desdichado
Hero
I ran an adventure who's plot was fairly loosely based on "The Shadow Over Innsmouth." Except that instead of being a seaside town, it was a mining town in the desert. PC's showed up--can't remember if they were just passing through or actually looking for someone there--and checked into the inn. Folks were all surly and strange. Most were cultists of some weird aberration--I remember using specifically the picture of the Beholder Overlord, but the stats were much lower, since my PCs wouldn't have been equipped to handle that. Several of the cultists had grafts and/or mutations that gave them weird spell like and supernatural abilities.
In any case, we didn't get much buildup of tension, sadly--one of the PC's immediately cottoned on that this was a desert version of Innsmouth and started causing trouble with anyone who even looked at him funny. To be perfectly honest with you, they got their asses handed to them by the cultists, ended up fleeing barely alive, dragging a comatose PC who had failed one to many Sanity checks, and had to live like outlaws for a while until they were strong enough to make another foray into town to go find who they were looking for.
Needless to say, I was using a D&D and CoC d20 hybrid rules wise. But I think the idea is still a sound one--find an existing Mythos story, summarize it's basic points in half a dozen or less single sentence bullet points, and you've got the skeleton already of a Mythos-like adventure. You probably want to swap out the existing Mythos creatures with something else, partly to make it less obvious to Mythos literate players and partly just to make it fit the theme of your campaign.
In any case, we didn't get much buildup of tension, sadly--one of the PC's immediately cottoned on that this was a desert version of Innsmouth and started causing trouble with anyone who even looked at him funny. To be perfectly honest with you, they got their asses handed to them by the cultists, ended up fleeing barely alive, dragging a comatose PC who had failed one to many Sanity checks, and had to live like outlaws for a while until they were strong enough to make another foray into town to go find who they were looking for.
Needless to say, I was using a D&D and CoC d20 hybrid rules wise. But I think the idea is still a sound one--find an existing Mythos story, summarize it's basic points in half a dozen or less single sentence bullet points, and you've got the skeleton already of a Mythos-like adventure. You probably want to swap out the existing Mythos creatures with something else, partly to make it less obvious to Mythos literate players and partly just to make it fit the theme of your campaign.