Plot

The movie begins with a scene set in 1974. A woman is boiling hot wax to make wax masks while her young son is eating his breakfast in a high chair. Suddenly the father comes in holding a near hysterical second son who is kicking and screaming wildly. The second child needs to be strapped down in his high chair due to his apparently violent nature, and is compared negatively to the other child.

The present. Six youngsters are on their way to a highly anticipated football game. Carly Jones (Elisha Cuthbert) is an ambitious young woman who is planning to move to New York. Her boyfriend Wade (Jared Padalecki) is a small-town boy who is hesitant about moving to the big city. They are joined on their trip by Carly's friend Paige Edwards (Paris Hilton) who may be pregnant with her boyfriend Blake's (Robert Ri'chard) child, although she hasn't told him yet. Blake has invited Carly's twin brother Nick Jones (Chad Michael Murray), a juvenile delinquent, to come along; Nick comments that their parents say Carly is the "good twin" and he is the "bad twin". Nick has brought along his rather annoying and immature friend, Dalton Chapman (Jon Abrahams). When night falls the group decides to set up camp for the night in a field. The campsite is visited by a mysterious stranger in a truck who shines his lights at the campsite, but refuses to leave, speak, or turn off his lights. Nick throws a beer bottle at the truck, breaking a headlight. Later that night, when everyone is asleep, Carly detects someone entering their camp.

The next morning Wade discovers that his fan belt has been torn... or cut. Carly and Paige, meanwhile, discover a large ditch filled with roadkill. A disheveled man with poor hygiene and strange behavior adds a deer to the pile. He offers to drive Carly and Wade to the nearby town of Ambrose to get a new fanbelt, while the rest of the group goes to the football game. However, the rest of the group soon find themselves in a traffic jam and decide to return to the camp site to wait for Wade and Carly to return from Ambrose.

Wade and Carly are creeped out by the roadkill transporter and get out and go to Ambrose on their own. The town seems almost like a ghost town, though the church is full. They visit the run-down wax museum, which is entirely made of wax. Scared by the rather eerie wax figures and the sudden appearance of a creepy man outside the window of the museum, Wade and Carly go to a garage where they meet with Bo, a mechanic who was in the church, who agrees to take them to his house and sell them a fanbelt. The handsome, charming man tells them the story of the Sinclairs (the former owners of the wax museum) while they walk to his house. Apparently Dr. Victor Sinclair and his wife Trudy moved to Ambrose when Victor was fired for performing experimental procedures on patients. Once in Ambrose, his wife Trudy discovered a passion for sculpting wax figures but eventually fell ill and died. A depressed Victor then committed suicide, leaving the Sinclair children as orphans.

While Carly waits in the car outside of Bo's house, she discovers that the headlight of Bo's truck is broken. Realizing it must be the same truck that bothered them the night before, she tries to warn Wade by blowing the car horn. However, as Wade is trying to leave, someone comes from below and cuts his Achilles tendon, crippling him. Wade is subsequently stabbed and knocked out. Revealing his true intentions, Bo begins chasing Carly, and she eventually ends up in the church and discovers that all the funeral guests she saw earlier are actually wax figures. She is captured by Bo and imprisoned in the cellar of his gas station with her lips glued together, as well as cutting a part of her finger off. Bo's brother Vincent (the creepy man Carly saw outside the museum), meanwhile, starts to embalm Wade in wax.

Nick and Dalton soon arrive in Ambrose to look for their friends and, upon encountering Bo, Nick asks him whether he has seen Carly or Wade. Carly hears Nick's voice and manages to rip her lips open and scream for help. Knocking Bo over, Nick rushes to the rescue and frees Carly. The siblings discover that the rest of Ambrose's population is dead, wax-preserved and displayed to make it appear that the town actually has living residents. At the same time, Dalton enters the house of wax and finds Wade covered in wax. Wade is alive, but unable to move. Dalton attempts to free Wade by peeling the wax. As he is doing this, he realizes that he is peeling Wade's skin off his face (which somehow fused with the wax). Vincent finds Dalton and starts to chase him, slicing off part of Wade's face off in the process which causes him to die from shock. Dalton falls down the stairs and Vincent decapitates him.

Vincent then goes to the campsite where Paige and Blake are and kills them by stabbing Blake in the neck and impaling Paige on a metal pole. Back in Ambrose, Carly and Nick overhear a conversation between Bo and Vincent, who are the Sinclair children seen in 1974. It turns out that Vincent (the "good" twin who was seen behaving well in the opening scene) simply wanted to continue his mother's work of creating wax figures but Bo (the "evil" twin who had been violent and was tied down in the opening scene) manipulated him to start murdering people to make more realistic wax figures out of their victims. Carly also finds newspaper cuttings that report how Dr. Victor Sinclair separated his Siamese twin sons at birth, leaving one (Vincent) badly disfigured. Chased once more by Bo and Vincent they eventually end up in the wax museum. Nick starts a fire in the house of wax and the whole house begins to melt. The demented brothers die in the fire, with Bo's head being beaten by Carly with a bat. Upon seeing Bo's lifeless body, Vincent, in anger becomes fixated on killing Carly, despite her trying to reason with him over his family's history of corrupt ways. Vincent is then stabbed by Carly and pushed through the wax floor to his death by Nick, where he lands on his brother's corpse on the same place where they were both conjoined. Carly and Nick then manage to dig their way out to safety through the second-story wall. The smoke from the blaze eventually draws outside help. The siblings discover that the town had long ago been abandoned, and that it was no longer on any map. As the ambulance carries Carly and Nick away, the Sheriff learns that there were actually three Sinclair children. The film ends with a shot of the roadkill transporter petting Bo and Vincent's dog and waving to Carly and Nick as their ambulance leaves Ambrose, leaving audience to think if the seemingly innocent man is one of the Sinclair brothers.