Susannah Kelton, a newly married twentysomething who was raised in foster care in the big city, learns that her real parents have died and left their property to her. She and her husband, Mike, travel to the island of Dunwich off the coast of Massachusetts to inspect the property. They find a local culture that is clannish, backward, and ignorant. The few friends they make amongst the locals, including Susannah's Aunt Agatha, warn them that the family mill is cursed and urge the Keltons to leave immediately and never look back.