Friends of friends emerge from the thick darkness, tattered and bloody, lucky to be alive, after narrowly escaping an ancient burial ground forgotten and buried underneath the marshes of Cape Cod. They've already lost two of the friends in the marsh deceased. They come across an empty Cape Cod vacation house alongside the marsh that is foggy and split into take shelter. Whatever was at the marsh continues to be after them and after one goes for help, the remainder of the group finds the evil at the marsh is not the one thing that wants them all dead. Something worse, some thing savage, lay in wait at the home. What happens next is unspeakable, terror that may not be unseen. These unlucky travellers spend their St. Patrick's Day trapped between 2 evils forcing them to fight, die, or go back the way they came.