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 is an ambitious young woman who is planning to move to New York. Her boyfriend Wade 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, who may be pregnant with her boyfriend Blake's child, although she hasn't told him yet. Blake has invited Carly's twin brother Nick Jones, 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. 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.
Wade finds his fan belt torn, or cut, the next morning. Carly and Paige, meanwhile, discover a large ditch filled with roadkill. A dishevelled man with poor hygiene and strange behaviour 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 campsite to wait for Wade and Carly to return from Ambrose.
The roadkill transporter terrifies Wade and Carly, prompting them to leave and travel to Ambrose independently. 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.
Carly notices a broken headlight on Bo's truck while waiting in the car outside his house. Realising it must be the same truck that bothered them the night before, she tries to warn Wade by blowing the car's horn. However, as Wade is trying to leave, someone comes from below and cuts his Achilles tendon, crippling him. Someone then stabs Wade, knocking him unconscious. Bo reveals his true intentions and starts chasing Carly. Eventually, she reaches the church, where she discovers that all the funeral guests she previously saw 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 having a part of her finger cut 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 realises that he is peeling Wade's skin off his face, which somehow fuses with the wax. Vincent finds Dalton and starts to chase him, slicing off part of Wade's face 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. Carly batters Bo's head with a bat as the demented brothers perish in the fire. 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 in the same place where they were both conjoined. Carly and Nick then manage to dig their way out safely 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 the audience to think if the seemingly innocent man is one of the Sinclair brothers.
Dahlia and her daughter Ceci—Cecelia— move to a flat in a condominium because of Dahlia's impending divorce. They live on Roosevelt Island, a New York neighbourhood. Because her soon-to-be ex-husband Kyle rejects the new school and the new surroundings, it looks like the proceedings for Ceci's custody are turning nasty. The mediators (Bill Buell and Linda Emond) feel that Ceci would be the most damaged person at the end of the divorce, regardless of who the custody winner will turn out to be eventually. Dahlia and Ceci live on the ninth floor. Dahlia tries to maintain her routines, such as reading children's books to Ceci before bedtime and taking her to school. However, she keeps on getting splitting headaches and has to take heavy medication. The condo has laundry facilities in the basement and a rude clerk called Veeck who is always complaining about everything but not doing much.
Pretty soon, Dahlia finds herself exhausted. She needs to keep her job to pay her bills; her mother disapproves of her life and finds herself worried about Dahlia's psychological strength. When Dahlia first looked over the flat, she didn't notice that there was a damp stain in a bedroom, but later on, when she and Ceci are already living there, it becomes a huge problem. They also begin to hear strange noises coming from the other side of the walls. The flat is badly lit, the same as the dilapidated corridors or the dark basement. The clerk promises to call in a plumber.
Two teenaged boys are making mayhem around the flat. They are almost always together, and they are considered vandals. One of them even makes a sexual remark to Dahlia when they find her in the basement preparing a washing machine full of clothes. However, they leave , and Dahlia is alone when she turns on the washing machine. It doesn't seem to work properly, so she starts another one. She hears strange noises; the water inside the washing machine turns nasty brown, and Dahlia thinks that there is a girl inside . She pulls the lid until the machine's door opens, but later, when she realises that there is nobody inside, she blames it on a prank played by the two teenaged boys.
Ceci has been unable to make friends in her new school, so she starts playing with her imaginary friend, Natasha. Dahlia attempts to remain calm, yet the burden of the world begins to weigh heavily on her. The clerk says that Ceci must have seen/heard Natasha, the little girl who lives on the 10th floor with her father. After the incident in the laundromat, Dahlia sees the red Hello Kitty schoolbag named after Natasha. When Ceci gives it back to the clerk, he just throws it away again.
Jeff Platzer is Dahlia's lawyer. He appears to live alone in his car. However, when Dahlia calls him in panic on a Sunday evening, he says to her that he is taking his family to the cinema and that he will call on her the next day. Cue to him, all by himself in the gritty cinema.
Dahlia talks to Ceci and tells her to stop playing with her invisible friend. Later, at school, Ceci is making a drawing of herself and her mother in front of the home. It looks like an invisible force is forcing her to paint on top of the drawing so that everything becomes a blurred disaster. Ceci gets annoyed and shouts to the invisible energy to stop it. The teacher sees that Ceci is having a kind of nervous breakdown. She takes Ceci to the bathroom so that she can wash her hands. There, muddy water goes out from all the taps, and Ceci encloses herself within a toilet cubicle. A dark-haired girl in a red coat walks by, splashing on the watery floor.
The teacher phones Dahlia, who arrives all wet from the heavy rain. She is told that Ceci got dizzy and fainted in the bathroom.
Kyle accuses Dahlia of being unstable and a bad influence for Ceci. Platzer asks Dahlia whether there is anything real in all those accusations, and Dahlia talks about her headaches. Platzer intervenes, sensing Dahlia's impending breakdown. He phones the owner of the building, Mr Murray, who seems really upset when he notices the level of damage made by the water coming from the 10th floor. Murray promises that a plumber will arrive the following day. The plumber says the pipes aren't the issue; there was no leak.
Dahlia decides to take her fears seriously and investigate the matter. She goes up to the 10th floor, but nobody lives there anymore.
On the 10th floor there lived a family of Russians. They were a dysfunctional family: the mother was an alcoholic, but their only young child, Natasha, was charming and welcoming. The mother checked herself into rehab, leaving Natasha with her father. The father returned to Russia, taking for granted that Natasha was with her mother. The child drowned in the reservoir after climbing the ladder on the roof, as both parents abandoned her. The clerk knew about it but did nothing since it wasn't his job. Instead, he just stopped taking care of the reservoir, and that was why Dahlia's apartment was getting flooded again and again.
Dahlia peers inside the reservoir. She immediately spots Natasha's corpse. Natasha opens her eyes and tries to take Dahlia inside, but Dahlia leaves the place and phones the police. The police arrest Veeck, but there is no way to prove that either of Natasha's parents killed her, and Veeck is probably only guilty of not having phoned the police when he realised that Natasha was dead.
Once the ordeal seems to be over, Dahlia talks to Kyle. She proposes reaching an agreement over Ceci's custody and living closer to Kyle. Kyle is overjoyed to hear it. Dahlia intends to leave the condo in only a week... for good.
That night, Dahlia prepares a bath with bubbles for Ceci. Dahlia leaves Ceci in the bath and talks on the phone to her mum. Dahlia is having her bath, playing with a blue doll. When Dahlia is about to take Ceci out of the bath, the girl is already in the living room, wrapped in a robe. Dahlia starts reading a children's book to her, and suddenly she realises that it is Natasha, not Ceci.
Dahlia has to break down the bathroom door. Natasha, a ghost, is trying to drown Ceci. To save her daughter, Dahlia offers to take care of Natasha forever. The bathroom becomes flooded.
The police are in the building again. They think that Dahlia has committed suicide. Kyle picks Ceci up and takes her to his home. When they are in the lift, they become stranded. At that moment, the ghost of Dahlia talks to Ceci, combs her hair, and tells her that if she has a problem in the future, Dahlia will be in the building waiting, and she will help her. Meanwhile, Ceci leaves the building happily, and Dahlia stays to take care of Natasha.
Urban legend: Bloody Mary
On November 5, 1969, three high school football players try to drug and kidnap their prom night dates. Their plan works with two of the girls, but the third, Mary Banner, tries to escape. The football captain chases her into a storage room and punches her, knocking her out. He panics and locks her body in a trunk, thinking she is dead. She wakes up later locked in the trunk, eventually dying inside it.
Three schoolgirls share this story during a sleepover 35 years later. One of them, Samantha, had written an article in the school paper critical of football players' academic achievements; subsequently, she, her friends, and her brother David were treated as outcasts by the rest of the school. Samantha, along with her two friends, Martha and Mandy, jokingly invoke Bloody Mary, only to disappear the next morning. After a day of absence, they awaken in an old mill. While most suspect a hoax on the girls' part, Samantha and David suspect that it is some prank on the football team's part.
While Samantha is haunted by visions of a dead girl bleeding from her head, several pupils die under mysterious circumstances resembling urban legends; for example, football player Roger burns in a sunbed. The next day, Heather, girlfriend to football captain Buck, has spiders erupting from a swelling on her cheek, driving her to cut her face with a mirror. The following evening, football player Tom is electrocuted while urinating on an old electrical fence, his ring finger being bitten or cut off.
Buck blames these deaths on the Owens siblings. Before her death, Heather made up with Samantha and tried to tell her that the incidents happened before. In her homework, Samantha finds notes sent to Heather about the disappearance of Mary Banner and the homecoming kidnappings of 1969, as well as notes referencing the events of the previous films. Browsing the school paper's archives, they find out that Mary was never found, that another victim committed suicide years later and that the third, Grace Taylor, still lives in town.
They visit Grace, who claims that Mary, or rather, her "life force", is exacting revenge on the children of the five people involved in the kidnappings but cannot (or will not) reveal the names of the perpetrators. Samantha is inclined to believe her, but David remains sceptical, thinking that Grace is more likely the killer. While sneaking around Grace's house, he also found out that Grace produced or collected artwork related to urban legends, and he identified Grace as the originator of the notes sent to Heather. The siblings go to warn Buck, who admits that he and his mates orchestrated Samantha's disappearance and blames her for the death of his friends. He also reveals that his father, the football coach, was one of the kidnappers in 1969 but didn't hurt Mary. Samantha, however, suspects that the coach killed Mary, as she saw him put flowers on her headstone earlier. Her stepfather, who overheard her, tells her to reveal any solid evidence she has.
Meanwhile, an upset Buck tries to relax by drinking and watching a movie in a motel. Falling asleep, he is awakened by the sound of dripping water and discovers the corpse of his dog. Mary attacks him, crawling out from under his bed and using her broken bottle to kill him. Different rumours about his death immediately spring up.
Both siblings are trying to find clues about the fifth remaining perpetrator, Samantha. One sibling is browsing through old photographs while David visits Grace again. Although Race continues to withhold the names, he guides David to the school archives. Going through the archives, he suddenly finds out the identity of the fifth person and rushes home but finds Sam gone and is suffocated by a hooded man. Meanwhile, Samantha is experiencing recurring visions of Mary, which reveal not only that the girl was alive when she was locked in the trunk but also her whereabouts. She also visits Grace, who tells her to find and bury Mary's corpse and reluctantly agrees to drive Samantha to the school. While Grace waits in the van, Samantha discovers a storage room and the trunk containing Mary's corpse. The hooded man also appears and enters the storage room, but Samantha locks him inside while carrying Mary's remains outside to the van.
Finding Grace asleep, Samantha drives the van to the cemetery, where she begins to dig a grave for Mary under her headstone. Her stepfather, whom Samantha had phoned, also appears and helps her dig but suddenly hits her with the shovel. Pursuing his stepdaughter through the graveyard, Mr Owens reveals that he was the one that locked Mary in the trunk and that he also killed his stepson, David. He finally captured her and is about to decapitate her when Mary, in her living form, appears. Smiling towards Samantha, she kisses him, then reverts back to her ghastly form and drags him with her into the grave.
When Samantha wakes up, the grave is surrounded by police and medical personnel retrieving her stepfather's corpse. They announce that Mr Owens suffered a heart attack while attempting to dispose of Mary Banner's remains.
Dr David Callaway, a psychologist working in New York City, decides to move with his 10-year-old daughter Emily to upstate New York after discovering his wife's body in a bathtub following her suicide. There, Emily makes an apparently imaginary friend she calls "Charlie". Her friendship with Charlie begins to disturb David when he discovers their cat dead in the bathtub, which Emily claims was a victim of "Charlie". Meanwhile, David suffers from nightmares of the New Year's Eve party that occurred the night before his wife died.
When a family friend, named Katherine, comes to visit David and Emily, Emily reveals that she and Charlie have a mutual desire to upset her father. Soon, they meet a man and a woman who are their neighbours. David is wary of their unusual interest in Emily. He later discovers that the reason for this is that the couple had a daughter who recently died from cancer and looks like Emily. Later, when David visits the woman, she nervously and ambiguously implies that her husband has begun abusing her in response to their child's death, emotionally and perhaps even physically.
David meets a local woman named Elizabeth and her niece, Amy, who is roughly the same age as Emily. Hoping to cultivate a new, healthy friendship for Emily, David sets up a playdate for her. Amy eagerly anticipates their immediate friendship, but Emily's act of cutting up Amy's doll's face spoils the playdate. After Amy runs out of the house, Emily tells David that she doesn't need any more friends.
Despite the unsuccessful playdate, David and Elizabeth hit it off. David invites her over to dinner one night, where Emily acts increasingly hostile towards her. Some time later, Elizabeth visits the house, hoping to make peace with Emily. When Emily tells her that she is playing hide-and-seek with Charlie, Elizabeth indulges her by pretending to look for Charlie. When she opens the closet, someone bursts out and pushes Elizabeth out a second-storey window to her death.
After the police discover her car crashed near David's house, David asks Emily what happened. Emily claims Charlie caused her death by pushing her out of the window and then tells David the location of her body. A terrified David discovers Elizabeth's body in the bathroom in a bathtub full of blood. David asks Emily where Charlie is, and Emily tells him that Charlie has just left.
David, armed with a knife, goes outside, where he meets a neighbour who has become friends with Emily. David assumes that his neighbour is Charlie, and he begins to act aggressively. Becoming suspicious that David has killed his daughter, the neighbour asks to see Emily, but David cuts the neighbour with his knife. The neighbour then calls the police.
Back in the house, David finds that, although he has been in his study many times (listening to his stereo and writing a journal), the boxes were actually never unpacked after the move. With this, David realises that he has a split personality and that Charlie is not imaginary at all, but that, in fact, "Charlie" is David himself. Whenever "Charlie" would emerge, David was in his study. Charlie, David's alter ego, was actually in control. David also realises that, under his Charlie personality, he killed his wife and then made it appear to be a suicide. He also fully recalls the events of the New Year's Eve party the night before his wife's death. Immediately after the countdown to midnight, David noticed his wife slip away. He followed her and caught her having sex in a stairwell with another guest. "Charlie" was created as a way for David's rage to destroy his wife, something that the docile David himself was too decent to do. Emily knew the entire time about her father's split personality but did not tell him to avoid freaking him out.
Once Charlie's identity and horrible deeds are realised by David, he becomes completely consumed by Charlie, leading him to murder the local sheriff, who arrives to investigate the previous altercation. Emily calls Katherine for help.
Katherine arrives and is pushed down the basement stairs by Charlie. Determined to play a hide-and-seek game with Emily once more, Charlie/David begins counting. Emily dashes and hides. She tricks Charlie and manages to lock herself in her room. As Charlie tries to break in, she climbs out from the window and runs into the cave where she originally met Charlie.
Meanwhile, Katherine takes the gun from the dead sheriff, breaks out of the basement, and finds Charlie looking for Emily in the cave. Charlie pretends to be David and attacks Katherine when she lowers her guard. Katherine begs for David to come out and fight his murderous other personality. Charlie tells Katherine that David no longer exists and that the moment David discovered the truth about himself, Charlie was able to fully take over. Emily emerges from her hiding place, begging Charlie to let Katherine go. Her distraction allows Katherine to shoot Charlie, killing him at last.
Sometime later, Emily is preparing for school in her new life with Katherine. But Emily's drawing of herself with Katherine has two heads, suggesting that due to the trauma of witnessing what happened to her father, Emily now also suffers from split personality.