In "Sinister," the new horror movie starring Ethan Hawke, a man explores the attic of his new home and finds a box of old Super 8 film reels. After his family goes to bed, he pours himself a whiskey and watches them: At first it's normal home-video sort of stuff, a family goofing around in their backyard on an autumn afternoon, and then it suddenly cuts to all of them, hooded, hanging from a tree.