Billy Lynch is a teenager living with his overbearing Aunt Cheryl, who raised him after his parents died in a car accident. Cheryl exhibits strange and increasingly possessive behavior towards Billy as he inches closer to adulthood, particularly as he starts to show interest in college and his girlfriend, Julie. Despite Cheryl's attempts to keep him close, Billy is determined to carve out his own life, but this causes tension in their household.

As Billy pushes for independence, Cheryl's behavior becomes more erratic and sinister. A series of violent and disturbing events unfold, drawing the attention of the authorities, particularly Detective Joe Carlson, who harbors his own suspicions about Billy based on preconceived notions. Billy finds himself caught in a nightmarish web of accusations, manipulation, and fear. Tensions rise, leading to revelations and confrontations that ultimately force Billy to confront the true extent of Cheryl's madness.