Dimensional Shamblers

It's the 1920s.  Or is it the 1930s?  We're not sure.  Doesn't matter.  Mankind braces himself for war whilst Eldritch forces stir restlessly beneath the Earth and malevolent intelligences glare down upon his fragile civilization from the lightless gulfs between the stars.  Here and there, scattered about this helpless little planet, handfuls of humans suspect the truth.  Some seek to ally