On Erin Island, an idyllic fishing village off the coast of Ireland, charming but somewhat work-shy Ciaran O'Shea, is tasked with greeting Lisa Nolan, a straight-laced young officer who has arrived from the mainland. Not that there is much for them to do, aside from dealing with the occasional drunk, and that's usually O'Shea himself.
But strange doings are afoot: the crew of a fishing boat disappears, whales start appearing dead on the shore, a local lobsterman catches a strange tentacled creature in his trap. Soon it becomes clear to O'Shea and Nolan that there's something big out there, and that it's hungry. It's time to rally the villagers, arm the troops...and head to the pub.