On the cusp of New Year's Eve, seven friends and a mysterious backpacker converge at a desolate ski lodge in the mountains when they are systematically hunted down by ruthless masked men with a cryptic agenda.

After his best friend dies in a racing accident, biking star Joe agrees to go back on the wheels for an exhibition in Chile. On a test run with his girlfriend Stephanie, they stumble upon a badly injured man dying from a mysterious virus. That's the start of a very bad day for them as they become the target of relentless killers ready to do anything to keep their secret to go out of the mountains.

After narrowly escaping an ancient burial ground, long forgotten and buried underneath the marshes of Cape Cod, a group of friends emerge from the thick, marshy darkness, tattered and bloody, lucky to be alive. They have already lost two of their friends in the marsh, presumably dead. They stumble upon an empty Cape Cod vacation house alongside the foggy marsh and break in to take shelter. Whatever was in the marsh is still after them and soon after one of them goes for help, the rest of the group learns that the evil in the marsh is not the only thing that wants them dead. Something worse, something more savage, was lying in wait just outside the marsh, in the house. What happens next is unspeakable, horror that cannot be unseen. These unlucky travelers spend their St. Patrick's Day trapped between two evils forcing them to fight, die, or go back the way they came.