In the beginning, we learn some more of the Texas Chainsaw Massacre's history. We learn that Sally Hardesty died of catatonia in 1977. We also learn that another family member that probably never appeared in the first one, W.E. Sawyer, of the cannibalistic clan was trialed and executed in 1981. During W.E.'s trial, the jury had came to the conclusion that since Leatherface was not taken into custody, they stated that it is unsure whether or not there is a Leatherface in reality. Now, taking place after the second movie, the year in the third installment is 1991. Chop Top didn't die at the end of Part 2 and is currently locked up in an asylum. Leatherface went off to live with some relatives along with Grandpa after the incident in 1987 as well. Leatherface continues along with his reign of terror as the killing machine he was before with the Sawyers keeping the Texas Chainsaw Massacre alive along with his relatives too.
In the opening scenes, a young couple, Ryan and Michelle, are traveling from California to Florida in order to return a car they borrowed from a close relative, but "there's roadkill all over Texas". They are soon stopped near the interstate at a checkpoint due to an old cemetery desecration, which turned out to be a mass grave of 40-70 bodies just thrown into the one big hole. They are confronted by a Texas State Trooper who permits them to carry on but warns them not to stop on the road for anybody.
After getting past the checkpoint, they stop at a service station owned by Alfredo Sawyer, a member of the cannibal family. After hitchhiking, Tex (a.k.a. Eddie Sawyer), stops at the service station as well, in time to give the kids some directions and to stop Alfredo from harassing Michelle who then gets in a fight with Tex saying that it's his place and he can do anything he wants to do there as he then grabs his shotgun and shoots Tex with it. As they leave the service station in a state of shock speeding away for dear life while they were shot at as well by Alfredo, Ryan tells Michelle that Tex gave him directions on where to go.
Little did they know, it would lead them to Leatherface while another family member, Tinker Sawyer, tracks them down and knocks them off the road with his large 4-Wheel drive vehicle!!! Once knocked off the road by Tinker according to the family's plan, Ryan and Michelle change a tire that had popped during their get away, but run into Leatherface in the process. They manage to escape, but even more in a state of shock and panic. Due to their reactions towards the family, they end up running off the road again by Tex Sawyer who had found his way into the middle of the road they were getting onto and get hit by another car.
The driver is a hunter and survialist by the name of Benny who recovers them from the scene of the crash and helps them. He tells them that his buddies were killed by the Sawyer family and he's out for revenge. After treating the couple, Benny heads on up the road back toward his truck finding Tinker who then tries to run him over. Benny jumps out of the way of Tinker's vehicle and falls down a hill nearby only to run into Leatherface. Benny fights off Leatherface and is saved by a young teenage girl who distracts Leatherface as Benny gets back on his knees. Leatherface ends up loosing the girl who goes back to be with Benny.
The teen girl says that she was part of a group of people who were killed by the family as well. Benny comforts her and then goes back to where Ryan and Michelle were, since they weren't moving as much after the accident, but Ryan and Michelle had taken off from that place leaving the young girl alone and defenseless as she is killed by Leatherface due to how protected she was. Ryan is killed by Leatherface as he falls into a bear trap set up by the family telling Michelle to leave as Ryan is impaled by Leatherface's chainsaw.
Michelle finds her way into a nearby house and finds a little girl who she follows to the girl's room. Once there, the girl shows Michelle her doll, Sally.... made out of the bones of a baby victim of the cannibal family!!!!! Michelle is all of a sudden grabbed by Tex who turns on the light in the girl's room revealing many human bones and remains as she is taken into the kitchen and nailed to a chair.
Meanwhile, Benny, still outside in the woods, finds Alfredo who is disposing human remains in a nearby swamp and knocks him into it. Ryan's body is taken into the house and hanged on a machine built by Tinker, who is the real "brains" of the whole family when it comes to manufacturing. Mama Sawyer appears, who is a crippled old lady confided to a wheelchair and speaks through a voice box, and who cares for the deathly pale Grandpa Sawyer.
(NOTICE: THIS NEXT SEQUENCE DESCRIBED IS DEPICTED IN ONLY THE UNRATED VERSION OF THE FILM! IF YOU DESIRE NOT TO READ THIS, SCROLL DOWN TO THE NEXT "NOTICE" I PLACED AT THE BOTTOM OF THE PAGE TO AVOID READING THE FOLLOWING EVENT IN THE PLOT AND TO ACKNOWLEDGE WHEN IT IS OVER DUE TO THE NEXT "NOTICE" POSTED ALERTING YOU!)
Later on, the little girl (a.k.a. Leatherface's daughter), kills Ryan off after he was hanging on the newly-improved meathook machine bleeding to death as the little girl pulls a lever that releases a sledgehammer, which whacks him in the face.
(NOTICE: THIS IS THE END OF THE DESCRIPTION OF THE UNRATED SEQUENCE OF THE FILM!)
Now almost supper time, Leatherface (whom the family refers to as 'Junior') tries out a new chainsaw given to him by Tex with "the Saw is Family" carved on the bar of the bright golden chainsaw on Michelle. Luckily, she survives as Benny arrives outside the kitchen window firing an automatic M-16 rifle at the house, killing Mama Sawyer, Grandpa Sawyer, and eventually Tinker Sawyer all present at the table ready to eat Michelle.
Michelle frees herself runs out of the house being chased by Leatherface and looses him as Tex swings an axe at Benny releasing gas from Tinker's car as Benny ignites up his lighter and throws it on the ground as it hits the gasoline killing Tex who burns to death.
Michelle ends up running back into Leatherface right when Benny hits Leatherface into a swamp saving Michelle. Leatherface ends up knocking out Benny as he falls to the bottom of the swamp. Leatherface then grabs onto Michelle dragging her into the swamp with her, but she hits him over the head with a rock knocking him out as well as he then sinks to the bottom too.
Michelle runs and finds a truck that belonged to Alfredo as it opens up and Benny gets out of the car and comforts her, but all of a sudden Benny is knocked over by Alfredo who is still alive due to only being thrown into a swamp. Michelle jumps into the truck, finds a shotgun, and shoots Alfredo with it killing him finally. Benny gets off his feet and gets back in the truck with Michelle as they drive off into freedom, but as this happens, Leatherface, who is still alive as well as his daughter, watches Benny and Michelle as they drive away.