Josh Riley knows his family's old house holds painful memories from the robbery, but he hates the gloomy place where they're living now. The rooms are too dark, and it always seems to be raining outside. Instead of reducing his anxiety, the new environment only makes it worse.

Besides his appointments with a therapist, school is the only thing that makes Josh feel normal. Seeing his best friends and his girlfriend, Emma, helps him forget his worries. Then he meets the new girl, Amanda Wolf, and all the tension returns. Her black makeup, piercing green eyes, and subtle smirk give him the creeps.

Shortly after her arrival, Josh begins to hear knocking at his front door after dark. Is it Amanda, the robbers from before-or something else? He tries calling the police, installing a surveillance camera, and even replacing the door, but still someone-or something-keeps pounding on the door and jiggling the knob.

Days go by with more questions than answers. Josh's parents are out of town, and his research keeps hitting dead ends. Then, one night when Emma has stopped by, she hears the knocking, and before Josh can stop her, she innocently opens the door...