Micah, a day trader, and Katie, a student haunted by a spectral presence since childhood, find themselves in a tumultuous relationship, playfully "engaged to be engaged." As Katie expresses concern that the ghost has followed her to their suburban San Diego residence, Micah decides to document their experiences by purchasing a video camera. This venture unfolds over three weeks, aiming to capture any paranormal happenings.
On a visit to their home, they receive a warning from Dr. Fredrichs, a psychic, who indicates that they are tormented by a demon that feasts on "negative energy" and is determined to haunt Katie, regardless of her location. He suggests they seek help from Dr. Abrams, a demonologist, but Micah's reluctance to reach out creates tension between the couple. Each night, Micah sets the camera on a tripod in their bedroom to record the events of the night, capturing strange occurrences such as objects moving inexplicably, lights flickering, and unsettling sounds ranging from whispers to ominous knocks.
As the nights progress, Katie experiences eerie behavior, often waking up to stand over Micah while he sleeps or wandering outside to swing alone in the backyard. Alarmingly, she is often unaware of these actions come morning. Tensions flare when Micah acquires a Ouija board, completely disregarding Dr. Fredrichs's warning against it. One of the pivotal nights sees the board's planchette move on its own, igniting a small fire despite the absence of an apparent cause, which sends chills down their spines.
In a panic, Micah attempts to gather evidence, scattering baby powder throughout the house to reveal inhuman footprints. While rummaging in the attic, he uncovers a charred photo of young Katie, a reminder of a fire that once consumed it. In an increasingly hostile environment, the bedroom door slams shut, accompanied by violent knocks that echo throughout the night. Following a second visit from Dr. Fredrichs, who senses a dark omen upon entering, the psychic departs, leaving Katie and Micah desperate for assistance.
One harrowing night, an unseen force drags Katie from the bed, and in a frantic bid to rescue her, Micah grapples with the entity's grip, only to discover horrific bite marks on Katie's back. The couple decides to seek refuge in a hotel, but an inexplicable urge compels a seemingly serene Katie to return home.
A chilling turn of events leads Katie to once more awaken and descend into the shadows, her screams piercing the silence of the night. As Micah rushes to her side, the camera captures the chaos of the struggle—until the sounds cease abruptly, replaced by the heavy thuds echoing up the staircase. Suddenly, Micah is hurled towards the camera, which tumbles to the ground, revealing Katie in a horrifying state as she approaches with a blood-soaked appearance and a twisted smile. In an instant, she lunges at the camera, and the screen fades to black.
An end title card chillingly announces that Micah's body was discovered days later, while the fate of Katie remains a haunting mystery. In an alternate ending, after the screams are silenced, footsteps lead to Katie’s eerie rocking in the aftermath. The police arrive to a scene of chaos, discovering the camera still rolling as they encounter a disoriented Katie, culminating in a shocking confrontation. The final title card pays tribute with the words, "Dedicated to Micah & Katie."
