Micah, a day-trader, and Katie, a student who claims that a ghostly entity has haunted her since her youth, are a young couple "engaged to be engaged". When Katie suggests the ghost has followed her to their two-story tract house in suburban San Diego, California, Micah buys a video camera in the hopes of capturing paranormal activity on film, a project that will ultimately last three weeks. Attempting to communicate with the entity is strongly discouraged during a visit to their house by Dr. Fredrichs, a psychic who assesses that they are being plagued by a demon which feeds off "negative energy" and is intent on haunting Katie no matter where she goes. Dr. Fredrichs also recommended the two contact Dr. Abrams, a demonologist, and Micah's reluctance to do so leads to frequent arguments between the couple. Each night, Micah leaves the video camera on a tripod in their bedroom to record whatever might be occurring while he and Katie sleep. He manages to document several phenomena such as objects moving on their own, lights and televisions switching on and off, and sounds ranging from voices and growls to footsteps and loud thuds. The strange occurrences in the middle of the night soon involve Katie awakening to spend several hours standing by the bed and staring at a sleeping Micah, and going outside to sit on the backyard swing. She ultimately does not remember her behavior the following morning.