The Sonman Mine Explosion

Literature isn't the only source of weird and wonderful events that could act as plot points.

In 1940, the Sonman Mine near Portage, Pennsylvania was the site of a large explosion that killed an estimated 63 miners. Rescue was severely hampered by a methane gas buildup that filled the tunnels, especially around the area called Right No. 16 heading where the explosion is said to have been centered.

While this can easily be explained as a gas explosion, it could also be a coverup for something far more sinister.

Mines can be a good source of mythos related investigations as you never quite know what could have been in those tunnels. In this case there are a few likely variants on this tale

1) The investigators are called in after the explosion to investigate some odd findings in the mining company's rescue attempts; possibly some body parts that couldn't possibly belong to any of the workers, or part of a strange carving.

2) The more fun one is to have the investigators called in to look at something uncovered in the tunnels during the mining. This could be something as simple as an odd mineral or some cave markings in a sealed cave; all the way up to carved tunnels uncovered during the excavation. To explain the disaster, you're likely going to want to have something really nasty hiding in there that needs lots of explosives to stop it escaping.

The Piltdown Man

While reading up on the various Lovecraft stories, I came across a reference to the Piltdown Man. This is a real life example of something that could hide deeper, darker things.

In 1908 a skull and jawbone were dug up in a gravel pit in East Sussex in England. This discovery was, for many years, believed to be an early, unknown strain of man as it had a distorted lower jaw. Part of the skull had been unearthed by workmen, with the other fragments discovered in the spoil heaps later. A reconstruction was undertaken by experts at the British Museum and given it's own classification, Eoanthropus dawsoni. Additional pieces, including the lower jaw and ape like teeth were discovered over the course of various digs at the site and added to the reconstruction. A second skull and jaw were said to have been discovered at Sheffield Park in 1915, proving that it wasn't just a one off. In our world it took until the 1950s to debunk the hoax as just a human skull with an orangutang jawbone and chimpanzee teeth.

During the course of WW2 it would still have been a hot topic for debate amongst anthropologists; but what if the final conclusion  published in Time magazine were to cover up something far more sinister?

While the original digs are too early for our time period, it would certainly be possible to have similar remains uncovered elsewhere, along with eerie inscriptions; leading to our intrepid investigators being sent off to recover the bones and hide any proof that they actually exist. this would be especially viable as we approach the end of the war and all indication of the elder races and their spawn are being covered up.