John Haloran has a heart attack. His wife Louise won't get any of the inheritance from his mother's estate if he is dead. She forges a letter from him to convince his family he's in NY on business to ensure a cut of the inheritance. His sister had also drowned and the family enact a morbid ritual in remembrance. She pays a surprise visit to her late husband's family castle in Ireland, but her plans become permanently interrupted by an axe-wielding lunatic who begins to stalk and murderously hack away at members of the family.