The film begins with Jennifer Hill driving to a shop to pick up the keys to a cabin she has rented for a few months and to get directions. She is going to the cabin in the woods down south in an unnamed Deep South state to write her second novel. On her way to the cabin, she gets lost and pulls into a gas station where she encounters a group of grease heads. She accidentally spills some fluid on the head of the group, Johnny, and hits the panic button on her car, scaring him. The other guys make fun of him for getting scared. Jennifer drives off into the gravel road to the cabin. A few days pass and nothing strange happens. One night, she begins to hear noises every so often that make her uneasy. Her first visitor is Matthew, a local simpleton handyman, who is sent to the cabin to fix the broken toilet. His reward is a kiss from Jennifer, and the shy Matthew runs out of the cabin. He later meets up with the group, and the guys begin to talk about Jennifer. They have a thing against fancy city girls who are too good for them.
Nightfall comes and Jennifer begins to hear noises around the house. She checks and finds nothing. But the next day, Jennifer's fears are realized when the gang from the gas station arrives at the cabin to get Matthew laid. After they mess with her, making her perform fellatio on bottles and a gun, she is able to escape the cabin and runs off into the woods. She bumps into the sheriff and Earl, the old man she rented the cabin from. The sheriff tells Earl to stay put while he brings Jennifer back to the cabin acting like he is going to help her. He finds wine and a joint and begins to interrogate her. After an improper pat down, the boys come through the door and she realizes that they are in cahoots. They hold her down, so Matthew can rape her. After he is done, she just gets up and walks out the cabin and into the woods. She is confronted by the gang again, this time they each have a turn raping her. The sheriff analy rapes her, She gets up again and walks out of the woods and onto a bridge. Just when the sheriff is going to shoot her, Jennifer jumps into the river. The gang searches for her body but have no luck finding her and begin to get rid of any evidence left behind.
A month passes before Jennifer returns. She has survived in the woods for a month eating, as she explains later, bugs and other things and has been staying in a run-down cabin in the woods. She starts playing games with the group who all think Matthew has lost it when they start to find signs of Jennifer around that appear to be left as a sign of the crime. Jennifer's first victim is Matthew, the slowest of the bunch who has a crush on her and is the only one that feels remorse for his actions. When she finally reveals herself to him in a cabin and invites him to sit on a couch next to her, he sobs and says he's sorry repeatedly as he clings to her waist and lies next to her. She listens for a time, then pulls a noose tight around his neck. As he struggles for air and again says he's sorry, her face crumples and she says that's not good enough, then drags him outside by the rope.
Her second and third victims are the group's two lackeys. Stanley, the fat one, steps in a bear trap, and Andy, who gets knocked out with a baseball bat. Jennifer uses fish hooks to keep Stanley's eyes open while she pulls out a fish and guts it, and spreads the guts all over his face. This is all being recorded on his camera; the same camera he used to film her being raped. The fish guts attracts crows, who begin to peck on his face and eventually his eye balls. Andy is tied up lying on a few boards over a bath tub being filled with water. Jennifer throws in some lye and removes one of the boards forcing him to use his strength to stay out of the base. Eventually his face hits the base filled bath tub. Each time he pulls himself up we see his base burned face, with his tongue dissolved.
The next day, Jennifer goes to the local gas station where she attacks and knocks out Johnny and brings him back to her cabin. There, she strings Johnny up by his wrists to the ceiling of the cabin, strips all the clothes off him and begins to pull out his teeth one by one with pliers. Then she pulls out the hedge clippers and cuts off his penis and sticks it in his mouth, leaving him to bleed to death.
After Jennifer is done with Johnny she goes to visit the sheriff's family. Pretending to be his daughter's school teacher, she talks to him on the phone. The sheriff races home to find Jennifer is no longer there. He finds out she has taken his daughter to the playground. The sheriff races there to find no one, except Jennifer in the back seat of his cop car.
After the sheriff wakes up from the blow from the tire iron, Jennifer talks about how nice his daughter seems and ignores for a while his entreaties not to hurt her, shoving a rifle barrel inside him as she tells him to imagine someone hurting his daughter the way they all hurt her. When he finally says, "She's an innocent girl!", she kneels beside him and says, "So was I.'' (Note: the movie never shows his daughter again after this point and it's assumed she simply let her go home, only using her to bait the sheriff.) She then reveals she attached a string to the trigger and the other end has been tied around the unconcious Matthew's wrist. She walks out of the cabin with the sheriff shouting for help and cursing her out at the same time. Then Matthew wakes up and inspite of a failed attempt by the sheriff to calm Matthew down, Matthew moves, firing the shotgun, killing both the sheriff and Matthew. In the final shot, the calm and still Jennifer is then seen sitting on a tree trunk outside the cabin, slowly smiling when she hears the shot and realizes they're all finished.