THE UNSEEN

After a hotel reservation mix up, two sisters Karen and Jennifer, and their friend Vicki Thompson, meet a friendly but shady character named Ernest Keller, the owner of a small town museum near Solvang, California. Ernest convinces the three women into accepting an invitation for cheap room and board at his large farmhouse outside of town, where he lives with his wife Virginia. Once there, Jennifer and Karen leave for the Danish cultural festival which Jennifer is completing a story on. At the festival, Jennifer is met by her estranged boyfriend, Tony, who gets her to stay behind to talk about their relationship.

Meanwhile, back at the house, Vicki prepares to take a nap in her room, but is attacked by an unseen figure. The figure eventually begins to pull Vicki into a floor vent; when she tries to escape, the grate of the vent slams down on her neck, killing her. At the parade, Karen leaves Jennifer and Tony to talk, and makes her way back to the house alone, where she too is then attacked and killed by the unseen, as it attempts to pull her by her scarf through a vent into the basement. Virginia, who had been in the barn slaughtering a chicken, soon after comes inside to find the bodies of both Vicki and Karen, and is distraught.

When Ernest arrives back at the house, he finds Virginia in shock over the murders. It is revealed that Virginia and Ernest are, in fact, brother and sister, and that Ernest had murdered his own sadistic father over 20 years ago in order to maintain his incestuous relationship with Virginia. They keep their inbred son named "Junior" locked up in the basement, where he is often viciously beaten by Ernest. Ernest convinces the subservient Virginia that Jennifer must be killed upon her return, in order to keep everything under cover.

When Jennifer gets back that evening, she is lured into the basement by Ernest, who locks her inside. She wanders around looking for a way out, only to stumble upon Karen and Vicki's dead bodies. In a panic, she is confronted by Junior, an intellectually disabled and infantile grown man. Junior attempts to play with Jennifer, but she is frightened by his rough behavior. Ernest comes into the basement to kill Jennifer, but Virginia, having had a change of heart, attempts to stop him. Ernest attacks Virginia, but Junior, enraged by the sight, intervenes to protect his mother. Ernest kills Junior by stabbing him in the head.

Jennifer escapes the basement, pursued by Ernest. Tony, who has returned to try to rekindle his relationship with Jennifer, tries to intervene but stumbles due to his leg injury. As Ernest is about to kill Jennifer, Virginia shoots him to death. She then returns to the basement to hold Junior's corpse.

Junior is killed during a fight with Ernest, who then attempts to murder Jennifer, but is stopped at the last moment.

The climax reveals the tragic dynamics of the Keller family, culminating in the death of their inbred son Junior at his father's hands. Ernest's pursuit of Jennifer is ultimately thwarted, bringing the cycle of violence and secrecy to a bloody close. The film ends with the survivor’s escape, underscoring the futility of the Kellers’ attempts to hide their monstrous legacy.