Some believe that on All Hallows Eve evil spirits are more easily able to cross over and torment the living. Unfortunately for the PCs, they are correct. From dusk to dawn on All Hallows Eve, the border to the nether realms is weakened and the dark horrors that roam there are more powerful.
This is a Call of Cthulhu (2nd - 6th Edition) scenario for 2-6 players where the PCs must figure out how to survive the night in a town into which horrors have been summoned. It was written as an entry into the RPGGeek Holiday Adventure Contest 2012.