Five teenagers, Erin, her boyfriend Kemper, Morgan, Andy, and Pepper, are on their way to a Lynyrd Skynyrd concert after returning from Mexico, where they were supplying themselves with drugs for the concert. As they drive through Texas, they spot a distraught hitchhiker, who eventually gets into their van.
After the startling shock, the group tries to contact the police, they then go to a store where a woman tells them the sheriff is at the mill. Instead of the sheriff, they find a little boy named Jedediah who tells them that the sheriff is at home drinking. Erin and Kemper go through the woods to find his house, leaving the other three at the mill with the boy. When Leatherface takes Kemper's body to begin to make a new mask out of him, he discovers a small black box from Kemper. Opening it, he discovers a ring. Kemper was intending to propose to Erin. Meanwhile, Sheriff Hoyt arrives at the mill and disposes of the hitchhiker's body, wrapping her in cellophane and putting her in his trunk. As he drives away, he tells the youths to leave. Erin arrives and finds that Kemper is still missing. Andy and Erin go back to the Monty's house, where Erin distracts him while Andy searches for Kemper. Monty realizes Andy is inside and summons Leatherface, who attacks Andy with his chainsaw. Erin escapes and heads towards the woods, but Leatherface slices Andy's leg off. Leatherface carries him to the basement and hangs him on a meat hook with his feet hanging over a piano, where he rubs salt on Andy's stump of a leg before wrapping it in butcher paper and tying it with human hair. Erin makes it to the mill and tries to escape in the van, but the sheriff shows up and, after spotting marijuana on the dashboard, orders Erin, Morgan and Pepper to get out of the van. Morgan, scared and disturbed by the sheriff's demeanor, and under pressure by Erin and Pepper, attempts to shoot the sheriff only to find the gun is unloaded. Erin gets the truck running and begins to drive, but one of the wheels falls off. Erin and Pepper stay still in the truck, but Leatherface appears on the top of the truck and tries to attack them by chainsawing the roof.
After witnessing Pepper's murder by Leatherface, Erin, who sees that Leatherface is wearing Kemper's face over his own, runs to escape and hides in a nearby trailer with two women inside, who offer her tea and try to soothe her. The two women, an obese middle-aged woman known only as the 'Tea Lady' and a younger woman named Henrietta, who is presumably her daughter, act strangely. Erin discovers they have kidnapped a child when she sees that the baby with them is the same child in a photograph with the woman who committed suicide earlier. However, the tea is drugged and she passes out when she tries to leave the trailer. Erin wakes up at the Hewitt house surrounded by the Hewitt family: Leatherface, his mother Luda May, Sheriff Hoyt, Uncle Monty, and the little boy Jedediah. Luda May tells Erin that her excuse for her son Thomas' actions is that her son was tormented by teenagers and that she felt no one cared for her family besides themselves. Erin is taken to the basement, where she finds Andy. She tries to help him off of the meat hook but when he sees he will land on the piano keys and alert Leatherface, he begs her to kill him, which she does, though suffering severe emotional trauma. Afterwards, she finds Morgan, who is still handcuffed. Jedediah, who clearly does not agree with the actions of his family, leads them out of the house. Jedediah rejects Erin's plea to come with them, rather staying there, and distracts Leatherface long enough for them to escape. Leatherface breaks in and discovers Erin, but Morgan attacks Leatherface, causing him to drop his chainsaw. Morgan grabs him and wrestles him, but Leatherface lifts Morgan upwards toward a chandelier, where Morgan becomes entangled by his handcuffs, and is left hanging and defenseless. Leatherface picks up his chainsaw, slicing up into Morgan's groin, killing him.
Erin runs out of the shack and escapes through the woods. Leatherface trips on a fence and cuts his leg while pursuing her. Erin finds a slaughterhouse and hides in a locker. Leatherface opens the locker across from hers and she attacks him with a meat cleaver, chopping off his right arm. Erin runs outside and flags down a trucker, whom she tries to convince to go away from the Hewitt's house. But he stops to find help at the eatery. Erin sees Luda May and watches as Sheriff Hoyt arrives and talks to the trucker. Erin sees Henrietta watching over the kidnapped baby in a highchair. When Henrietta walks outside to join Luda May and Sheriff Hoyt, who are talking to the truck driver, Erin sneaks the baby out of the eatery and places her in the sheriff's car and upgrades it.