After barely escaping from an ancient burial site hidden beneath the Cape Cod marshes, a group of friends emerges from the dense, swampy gloom, battered and bloodied, grateful to be alive. They have already lost two companions in the marsh, presumed dead. They come across an unoccupied vacation home near the misty marsh and break in to seek refuge. However, whatever pursued them in the marsh is still on their trail, and soon after one of them leaves to find help, the remaining friends discover that the malevolent force in the marsh isn’t the only threat. Something even more terrifying and brutal awaits them just beyond the marsh, inside the house. What follows is an indescribable horror that cannot be forgotten. These unfortunate travelers find themselves spending St. Patrick’s Day trapped between two malevolent forces, leaving them with no choice but to fight, perish, or return the way they came.