EricW

What an interesting character - From Wikipedia; During the following decades, various groups mounted several rescue expeditions, without success. They heard only various rumours that could not be verified. In addition to reports that Fawcett had been killed by Indians or wild animals, there was a tale that Fawcett had lost his memory and lived out his life as the chief of a tribe of cannibals. 

An obvious plot point, what would one of the rescue missions which were sent do if they found Fawcett had become the cannibal leader of a degenerate Cthulhu tribe? Would they be more interested in preserving his reputation than his life?

Indiana Jones territory :-). Lots of interesting things happening during that period, the British Empire reached its greatest extent in the 1920s, the post WW2 collapse was still in the future - though Britain was facing increasing challenges from imperial Japan and the United States, and rocked by rising independence movements. Russia and China were in poor shape, though who knows - the new Soviet government may have had some interest in British dominions. Germany was in chaos in the 1920s, mostly inward looking, Hitler didn't arrive until the 30s. Prior to the great Wall Street Crash of 1929, America and to a lesser extent other Western countries were in a state of economic exuberance, lots of cheap money sloshing around financing all manner of ill considered projects. 

Who knows what hideous survivals of the pre-human past took advantage of the raucous disorder, to feast on the vulnerable?

How about being pursued by something almost human?

It's no accident some of the scariest Lovecraft stories are stories which involve protagonists which are or which try to seem almost human - stories like Shadow Over Innsmouth, The Lurking Fear, The Whisperer in the Darkness, etc.

There is a well known phenomenon in robotics called the "uncanny valley". We can accept creatures which are not human. We can accept creatures which seem totally human. But we reject creatures which seem almost human - our minds have difficulty coping with the subtle dissonance of something which tries to seem human, but doesn't quite get it right.

The use of "Humanity" as a measure of psychic sensitivity is interesting.

In the original story CoC artists were more sensitive to the call than doctors, lawyers or scientists. So it is understandable that artists who spend all their time exploring feeling and sensation would be expected to be more "in tune" with the cosmic ummah.

But in many of the stories, such as "The Dreams of the Witch House", increasing exposure to mythos elements is the driver of psychic sensitivity, of greater awareness of events occurring beneath the surface of reality, many of which could be considered psychic in nature.

In addition, there is no suggestion in CoC that had Cthulhu remained at large, psychically sensitive people driven into performing barbaric acts of insane bloodletting, which would surely have shredded any humanity in them, would have somehow lost their ability to hear his call.

So I suggest that mythos skill should surely be the dominant determinant of "psychic sensitivity". A "humanity" skill might well provide an initial measure of predisposition to sensitivity to psychic events, but as soon as some mythos skill is acquired, surely that would dominate?

Why not go straight to the original source material? This story is about Yuletide, but it could be adapted to Halloween.

http://www.hplovecraft.com/writings/texts/fiction/f.aspx

It might be fun to throw a lot of red herrings. I mean, this is Innsmouth right? The players will be totally paranoid - there is no end of suspicious characters they could encounter.

How about the missing cats - and the nasty old woman who poisons the local cats, and throws them in her trash, because she's a bird lover.

The local librarian who has a collection of mouldering ancient occult books, who leads a coven of would be witches - but who has no mythos knowledge whatsoever.

The missing kids (they ran away together because their strict religious parents didn't want them to see each other).

The police officer who mostly does a good job, but has a nasty secret fetish - he likes touching ladies underwear (lurking suspiciously in the back yard of an attractive woman - maybe thats his next sacrificial victim!). 

The genuinely kind elderly priest who truly believes in his religious mission, and goes out of his way to welcome strangers and show Christian hospitality.

How many illegal acts could you tempt the players to perform, because they are acting like paranoid power gamers, instead of genuinely roleplaying their part?

Of course, once the players finally settle down, and get fed up with jumping at shadows, then they're in real trouble.

Who did they miss? The answer is the polite young female doctor who patches up their wounds from all these silly scrapes. She is actually a mad cultist who wants to join the deep ones - but she didn't have the right ancestors. So she's been secretly cooking up a hybridised virus, to alter her personal DNA, to achieve personal immortality and live forever in eternal bliss beneath the sea. The virus is contagious, and will spread like wildfire once it is released, causing hideous genetic changes in anyone who contracts it - but she doesn't care about that. All she needs to complete her work are a few test subjects, say a strange group of disposable out of towners, whom nobody likes and nobody will miss.

Of course, at first the doctor will ignore the players, and they will ignore her - when the players say "OK, we go to the local doctor to get this broken arm treated...", she will just be one of the local town doctors. But after a few visits, perhaps one of the players will ask her out on a date...

Reading the encounter between the crew of The Vigilant and Cthulhu, while most of the crew were killed by violence, died of fright, or went hopelessly insane, Johansen was able to act rationally. He went into shock after the encounter, but he retained his sanity, albeit with horrible memories of the encounter. So I think there is a case for allowing a small chance for players to somehow hang onto their senses no matter how horrific the encounter. 

http://www.dagonbytes.com/thelibrary/lovecraft/thecallofcthulhu.htm

Three men were swept up by the flabby claws before anybody turned. God rest them, if there be any rest in the universe. They were Donovan, Guerrera, and Angstrom. Parker slipped as the other three were plunging frenziedly over endless vistas of green-crusted rock to the boat, and Johansen swears he was swallowed up by an angle of masonry which shouldn't have been there; an angle which was acute, but behaved as if it were obtuse. So only Briden and Johansen reached the boat, and pulled desperately for the Alert as the mountainous monstrosity flopped down the slimy stones and hesitated, floundering at the edge of the water.

But Johansen had not given out yet. Knowing that the Thing could surely overtake the Alert until steam was fully up, he resolved on a desperate chance; and, setting the engine for full speed, ran lightning-like on deck and reversed the wheel. There was a mighty eddying and foaming in the noisome brine, and as the steam mounted higher and higher the brave Norwegian drove his vessel head on against the pursuing jelly which rose above the unclean froth like the stern of a daemon galleon. The awful squid-head with writhing feelers came nearly up to the bowsprit of the sturdy yacht, but johansen drove on relentlessly. There was a bursting as of an exploding bladder, a slushy nastiness as of a cloven sunfish, a stench as of a thousand opened graves, and a sound that the chronicler could not put on paper. For an instant the ship was befouled by an acrid and blinding green cloud, and then there was only a venomous seething astern; where - God in heaven! - the scattered plasticity of that nameless sky-spawn was nebulously recombining in its hateful original form, whilst its distance widened every second as the Alert gained impetus from its mounting steam.

 

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