In 2006, Katie (played by Katie Featherston) and her boyfriend, Micah (Micah Sloat), are a young couple who recently moved into a two-story tract house in suburban San Diego, California. Katie claims that an "evil" presence has haunted her since childhood and believes that it has followed her to their new home. Each night, Micah mounts a Sony HDR-FX1 on a tripod in their bedroom to record any paranormal activity that might occur while they sleep, in the hopes of solving the problem himself. The first night, the only thing they catch are footstep noises and the sound of keys dropping, which they find on the floor downstairs the next day. Katie hires a psychic, Dr. Fredrichs (Mark Fredrichs), who assesses that she is being haunted not by a ghost, but by a demon. He says the demon feeds off negative energy, and its intent is to haunt and torment Katie no matter where she goes. He advises them not to taunt or communicate with the demon, and to contact demonologist Dr. Johann Averies for help. Though Katie seems interested and engaged in the situation, Micah does not take it seriously.
The camera captures several supernatural phenomena which remain minor at first, such as a light turning on and off in the hallway during the second night, and the bedroom door moving by itself during the third night. During the fifth night however, Katie wakes up from a nightmare and it is revealed that something was whispering to her in her sleep according to the paranormal psychic. Micah begins to taunt the demon and the phenomena worsen; During the tenth night, the demon crawls through the covers and when Katie is woken up by it she hears growling in the hallway. She investigates but it runs downstairs. During the thirteenth night, they are awoken by a supernatural screech and a loud thud. They go downstairs to investigate and find the chandelier moving by itself. During the fifteenth night, Katie awakens and spends several hours standing by the bed staring at Micah while he sleeps, before going outside to sit on the backyard swing. Micah awakens by noises in the hallway and tries to convince Katie to come inside but she refuses. When Micah goes inside to get her a blanket, he finds the TV turned on in the bedroom and the kitchen sink tap on and is then startled by Katie, who followed him inside but says that he woke her up. Katie remembers nothing the next day.
Katie, already irritated by Micah's flippant response to the situation, becomes irate when Micah brings home a Ouija board despite Dr. Fredrichs' warnings. The two go out of the house that evening, leaving the Ouija board in the living room. The curtains and plants start to blow around and the Ouija board's planchette moves on its own. A small fire erupts on the board, but it extinguishes itself before they get home. It seems that the board has left them an unrecognizable and unreadable message. During the sixteenth night, the bed tips over. During the seventeenth night, Micah sprinkles talcum powder in the hallway and when the couple is awoken by noises, they find non-human footprints leading to the bedroom from the attic. In the attic, Micah finds a burnt photograph of a young Katie, which was previously thought to have been destroyed in an unexplained house fire.
The next night, a light turns on and off and the bedroom door slams shut. Loud banging is heard, as something is apparently trying to get in. They discover that the glass over a photo of them has been smashed, with Micah's image scratched. Dr. Averies is abroad when Micah finally agrees to invite him, so Dr. Fredrichs comes instead. Upon his arrival, Dr. Fredrichs immediately has a sense of dread. He apologetically leaves despite their pleas for his help, stating that his presence is only making the demon angry. During the nineteenth night, a shadow moves across the bedroom door. Katie is pulled out of the bedroom by an unknown force during the twentieth night. Stressed and exhausted, the couple decide to go to a hotel. Micah finds Katie gripping a cross so tightly that it bloodies her palm. Micah, angry at the situation, burns the cross and the picture found in the attic. Just as he is set to leave, Katie insists that they will be okay now, her voice flat.
The next night Katie comes out of bed and stands beside it staring at Micah for approximately two hours and then walks downstairs. After a moment of silence, Katie screams Micah's name, waking Micah who rushes to her. The camera records Katie screaming incessantly. Then Katie's screaming stops and a brief silence is followed by the sound of heavy footsteps coming up the stairs. After another brief silence, Micah's body is violently hurled at the camera, knocking it over sideways and revealing Katie standing in the doorway. She then slowly walks into the room, her clothing soaked with blood. Crouching over his body, she sniffs Micah (who has evidently been murdered) and then slowly looks up at the camera with a sly smile. As she lunges toward the camera, her face takes on a demonic appearance just as the scene cuts to black. An epilogue text states that Micah's body was discovered by the police on October 11, 2006, and that Katie's whereabouts remain unknown.
[edit] Alternate endings
In its original version, the film featured a different ending, in which Katie was seen getting killed, contrarily to her unknown fate featured in the theatrical version. In this version, after going downstairs on the final night and waking Micah with a scream, only Katie is shown returning to the bedroom, holding a large bloody kitchen knife, her shirt bloodied. She sits beside the bed, holding the knife and rocking herself, until about 2 p.m. the next day, when her friend Amber calls and leaves a message expressing her concern. At about 9:20 p.m. that night, Katie is still sitting and rocking by the bed, and Amber can be heard entering the house. During this short period, Katie stops rocking, but when Amber screams (evidently after finding Micah's body) and runs out of the house, she resumes her motion. Half an hour later, just after 9:50 p.m., police enter the home and discover Micah's body as well. As they are checking Micah for vital signs, a light turns on in the bedroom down the hallway, but before the police see it, the light turns off again. They discover Katie, still sitting beside the bed with the knife. As they call to her, she wakes from her catatonic state and seems confused. As she approaches them, knife in hand, calling Micah, they ask her to drop the weapon. Suddenly the bedroom door behind the police officers slams shut, startling them and causing them to shoot Katie, who collapses on the floor. The police then call dispatch and check the bedroom at the end of the hall, but find nothing. They discover the video camera, still running. A dedication to and a picture of Katie and Micah are then shown. The original ending for the film was available for a time for viewing on the Internet before Paramount exerted a claim of copyright on the material.[13]
Once Paramount acquired the film, two new endings were developed for the film, one of them being the one seen in theaters. The scrapped ending was shown at only one public viewing and was later offered as an alternate ending on the DVD and Blu-ray releases of the film.[13][14] In this ending, Katie gets out of bed and stands staring at Micah, as she did in the theatrical ending, except she does not move to Micah's side of the bed. About three hours pass, then she finally goes downstairs. She lets out a blood-curdling scream, which wakes Micah up and he runs downstairs. The screaming continues, and the sounds of a struggle are heard before the noises abruptly stop. There is silence for a short while before loud footsteps are heard on the stairs. Katie then walks into the bedroom, Micah's blood covering her shirt, with a knife in her hand. She closes and locks the bedroom door, before walking up to the camera, standing idle briefly. She then lifts the knife and slits her own throat, then falls to the floor, dead.
