The woman at the center of the story is named Sarah, a shy and unassuming high school student who becomes the unwitting host for a parasitic alien creature. As the creature begins to exert its influence over Sarah, she starts to experience vivid and terrifying hallucinations, which she tries to dismiss as mere nightmares.
But when Sarah gets pulled into the orbit of a group of cheerleaders who worship Satan and regularly engage in brutal, ritualistic killings, she realizes that her nightmares are all too real. As the cheerleaders begin to target Sarah and her friends for their next sacrificial victims, Sarah must fight to regain control of her mind and body before it's too late.
Meanwhile, a team of government agents is tracking the alien creature that has taken over Sarah, hoping to capture it and learn more about its nature and origins. But as the agents get closer to their target, they realize that they may have underestimated the deadly power of the creature and its ability to manipulate and control human hosts.
