For Katie (Katie Featherston), a San Diego college student, things have been going bump in the night since she was eight years old and a ghost attached itself to her. The unseen being that has been benignly haunting her for years thrills Katies loving but skeptical boyfriend, Micah (Micah Sloat), who sets up a video camera to capture any supernatural goings-on. For his debut feature, reportedly shot in seven days at a cost of 15 grand, writer-director Oren Peli works wonders with stationary camera footage of the sleeping couple: The bedroom door moves, slightly; lights in the hallway go on and off; a shadow passes the bed. As the nights go by, the presence, seemingly annoyed at being recorded, begins upping the ante, and soon it appears that poor Katie is on the verge of channeling her inner Linda Blair. Grounded by strong performances by newcomers Featherston and Sloat, who pretty much have the movie to themselves, Paranormal Activity, which demands to be seen in a crowded theater, is refreshingly blood-freethe fact that its old-school scares caused seemingly jaded twentysomethings at a recent midnight screening to squirm in their seats suggests that theres hope for the world after all.