For siblings Brie, Daniel, Crew, and Jess, family has always come first. But when Crew (Daniel DiTomasso) invites his girlfriend Sara (Kate French) into the family, distrust begins to bubble between the siblings. Seeing Sara as a threat, Brie (Fiona Dourif) grows spiteful and increasingly suspicious that she is being replaced. That is, until the night Crew attempts to murder her in their family house. Traumatized, Brie is sent to a mental facility where she is tormented by hallucinations of Crew from the night of the attack. But when the visions begin to bleed into reality, Brie starts to fear that it's not just her sanity that's in danger, and she flees the facility. In a frantic attempt to return to her remaining siblings and warn them, Brie begins to uncover a trail of gory, sinister secrets that lead her to believe that she might not know her family as well as she thought.