In Pasadena, California in 1969, a young Mexican couple rushes to the home of medium Shaun San Dena (Flor de Maria Chahua). Their son had stolen jewelry from a group of Gypsies three days prior, and since then, has been complaining of seeing and hearing things not of this earth. San Dena tries to help the boy in a seance, but she and the boy's parents can only watch in horror as the boy is thrown from the balcony by an unseen force before being pulled into Hell by demonic hands. The spiritualist vows that she will meet this demon again one day.
Forty years later, Christine Brown (Alison Lohman), a loan officer at a local bank, is working in her office and desperately hopes to be promoted to assistant manager. Christine's boss, Mr. Jacks (David Paymer), tells her that the position has come down to her and the new guy, Stu Rubin (Reggie Lee). He advises her that she needs to demonstrate that she can make tough decisions when she needs to. On her lunch break, Christine visits her boyfriend, Professor Clay Dalton (Justin Long), in his office. Christine gives Dalton a rare coin she found at the office in circulation. Clay puts it in an envelope and puts it in his bag. When Christine leaves, Clays mother calls and tries to set Clay up with a girl who she feels is better for Clay than Christine. Christine hears this from the hall and leaves dejected, feeling that she is not enough to get what she wants (the guy, the job, etc.) Christine returns to work and sees Stu bribe Mr. Jacks with Lakers tickets. Later that day, Mrs. Ganush (Lorna Raver), an elderly gypsy woman, asks for a third extension on her mortgage because she is struggling with economic problems due to an illness. To prove herself to Mr. Jacks, Christine, against her better judgment, denies Mrs. Ganush the extension. In desperation, Mrs. Ganush prostrates herself before Christine, begging and kissing the hem of her skirt. Christine panics and shoves the woman away while calling for security, shaming her in public. As security guards escort Mrs. Ganush out, Mr. Jacks compliments Christine on how she handled the situation and implies that if she can close another big loan, the assistant manager position will be hers.
Mr. Jacks compliments Christine on how she handled the Ganush situation. He tells her that shes close to getting the promotion but has to seal the deal on a certain loan that is in limbo at work. Pleased, she walks to her car with her file and some office supplies. She walks out and sees Mrs. Ganushs car parked across from her own. She gets in her car and Mrs. Ganushs scarf is blown onto the windshield freaking Christine out. Christine turns around to follow the scarf and sees Mrs. Ganush behind her. Mrs. Ganush attacks and the two fight before Christine is able to lock Ganush outside of her car. Christine screams HA I BEAT YOU BITCH, before Ganush breaks the window with a cinder-block and drags Christine out. Ganush takes a button from Christines coat and mutters an incantation before handing back the button and disappearing.
The police arrive to investigate the incident and Clay arrives to drive her home. On the way, Christine hears a strange whispering and decides she wants to get her fortune told. Clay is skeptical as to the legitimacy of the fortune teller and trades jabs with the spiritualist, Rham Jas (Dileep Rao). Rham says hell read her fortune for $60. However, during the reading, Rham is greatly disturbed by the mental appearance of the demon which makes him end the session. He gains Christines trust by telling her that he knows about the button. Clay drives Christine home and leaves to get something from his office. Alone at home, Christine bakes a cake in her kitchen and plays with her kitten while waiting for Clay. She looks in a cookbook and sees a picture of her winning a dessert contest as a teenager and she is very overweight. She crumples up the photo and throws it out to continue baking. While still baking, all the lights go out and Christine is left alone in the dark. Her gate starts creaking and she sees a silhouette of a goat's head on the wall which then throws her into the cabinets causing minor injuries. Clay arrives home and assumes that Mrs. Ganush followed them and attacked Christine again. However, when she insists that no one attacked her, they contact a psychologist. After a quick visit from the psychologist who says that victims of assault often relive past trauma, Christine calms down and they go to bed. She has a very disturbing dream which involves a fly and being attacked by Ganush. She wakes up screaming, alarming Clay. Christine says it was only a dream and goes to work.
At work, Christine is approached by Stu, who wants to learn about the loan guidelines of the branch. As she starts to explain she has a flash to Ganushs visit. Mr. Jacks comes over to calm her down, but Christine gets a bloody nose which then turns into a hemorrhage that covers Mr. Jacks in blood. Christine leaves the bank while everyone is left wondering what is going on. When no one is looking, Stu steals the files for the big loan Christine is working on.
Christine goes to the house of Ganushs granddaughter, having gotten the address from Ganushs papers. The granddaughter doesnt want to let her in, but Christine says that she wants to make things right. The granddaughter lets her in and tells her to go down the hall to the left. Christine walks in on a bunch of gypsies sitting around eating together and sees that this is the wake for Ganush. Christine falls on the body, which rolls and spews embalming fluid all over Christines face. Ganushs granddaughter says that Christine deserves what is coming for her.
Christine goes back to Rham seeking guidance. Rham tells her that the demon coming for her is called the Lamia. He tells her that Ganush cursed the button from Christines coat and that in three days the Lamia comes to take the soul of the person who owns the button. He speculates that a sacrifice to appease the Lamia may be able to convince the demon not to take her soul. He gives her a book on animal sacrifices but Christine tells her he wont do it. You will be surprised by what you will be willing to do when the Lamia comes for you he retorts.
Christine goes home and is stalked by the shadow of the Lamia. It comes for her and throws her around the room and throws her against a few walls before throwing Christine into her Dresser. Christine freaks and grabs a kitchen knife and calls for her kitten.
Christine is burying her dead kitten when Clay arrives. Clay asks why she has blood on her arm, but Christine shrugs it off and tells Clay that everything is fine now. They go and have dinner at Clays parents house. Christine gives them a harvest cake, which she learned how to make when she grew up on a farm. Clays mother talks down to her until Christine shows that shes smart and capable and brutally open about her past. She reveals that she doesnt talk to her mother because, after her father died, her mother became an alcoholic and doesnt want to see anyone. This impresses Clays mother since her father was also an alcoholic but she never told anyone. The group enjoys the cake while Christine starts seeing an eyeball in hers. She stabs it and it bleeds and she fakes putting a piece of cake into her mouth to put on a show, but she then coughs up the fly from her dream. This disgusts Clays parents, who think the cake has flies in it. To make matters worse, the Lamia starts to bang on the door, causing Christine to freak out. She leaves and Clay tries to follow but his parents tell him he cant help her because she is ill.
Christine consults Rham Jas again, who tells her that there is one person who can help her fight the Lamia but that this person will only do so for $10,000 dollars. Christine immediately takes everything she owns of value to sell but only comes up with $3,500. She goes to Mr. Jacks to ask for a $10,000 dollar advance on the Assistant Manager position, but Mr. Jacks tell her that the loan she was working on fell through since another bank was able to undercut them. He tells her he will have to investigate and then gives the Assistant Manager position to Stu. She leaves the office angrily and goes home.
Clay arrives to find her eating a pint of ice cream in her kitchen. He tells her that the second he knew he loved her, he swore hed do anything to protect herso he paid the $10,000 dollars.
Clay drives her to the house of Shaun San Dena and Christine goes in alone. Shaun wants to host a séance to draw the spirit into the physical realm in order to kill it. Shauns assistant brings a goat into the room so that they can force the Lamia into it. Shaun tells Christine that once Shaun is possessed, Christine must put her hand on the goat to draw the Lamia out. Shaun, Rham, Christine and the assistant begin the séance. They use an incantation to bring it forth but manage to summon a group of lost souls. Shaun banishes them before realizing the Lamia is coming. The Lamia possesses Shaun and addresses the group. It tells them it will take Christine to hell, where it will feast on her soul. Christine grabs Shauns hand and forces it onto the goat. The Lamia gets angry and starts screaming. The assistant tries to use a machete to kill the Lamia, but the Lamia moves, the machete misses and the Lamia bites the assistant.
Christine goes to help the assistant but he is revealed to be the new host. It starts mocking Christine and a mini fight ensues. Rham is knocked out by a chair and Shaun is in a trance. It summons flames and dances over the table. It tells Christine it doesnt want her cat, and draws the cat out of its mouth and throws it at her. He tells her that hes going to enjoy feasting on her Porker soul. Shaun breaks out of her trance and uses a powerful incantation to banish the Lamia from the séance. She collapses and dies immediately after. Christine takes this to be a great irony, in that Shaun waited 40 years for a rematch with the Lamia and beat it on her last night alive, but Rham interjects. He tells her that the Lamia is not banished and that Shauns death proves that nothing can stop the Lamia. Rham tells her that the Lamia is coming for the owner of the buttonand that her last hope is to make a gift of it. He takes out an envelope and has the button sealed in it. He tells her that whoever she gives the button to, she curses to hell and that the reason Rham didnt tell her was because he didnt want to be her accomplice in sending someone to hell.
Christine gets in Clays car and tells him its over. They almost hit an old man (who appears to Christine as Ganush) and the old man tells Christine that shes going to hell. Christine drops the envelope with the button and Claytons bag opens and spills his papers over her envelope. Christine freaks when she cant find it but grabs the envelope that has a circular shape inside. Clay drops her off at home and tells her to meet him at the train station so they can go to his parents cabin.
She goes to an all night diner and drinks a ton of caffeine and struggles over whom to give the button to. She calls Stu and tells him to meet her otherwise shell tell Mr. Jacks that Stu gave her loan papers to the other bank. He meets her and begs her not to tell Mr. Jacks. She is about to give him the button but decides against it.
Christine asks Rham if the cursed object can be transferred to the dead. Rham says that while Gypsys place good luck wishes on the dead, formal offerings can be made. He tells her Yes. Christine drives to the cemetery and digs up Ganush. She Takes the envelope, makes a formal offering and shoves it down Ganushs throat. The rain fills the grave with mud and Christine almost drowns but she makes it through.
The next morning, Christine goes to meets Clay at Los Angeles Union Station, they have plans to spend a relaxing weekend in Santa Barbara. She is wearing a beautiful new coat and walks up to Clay. Clay is on the platform checking his ring box, mentally prepping for a proposal. He notes the new coat and asks Christine what happened to her old one. Christine tells him she threw it out and before she can elaborate, Clay tells her its unfortunate and gives her the envelope with the button in it. She had dropped it in his car the night before and accidentally picked up a similar one, which contained the rare coin she gave to Clay. Horrified, Christine panics and walks backwards from Clay and falls onto the train tracks. Clay starts yelling for help and, as the train approaches, the ground starts cracking around her. As Clay looks on, demonic arms pull her down and Christine is brutally dragged to hell screaming to Clay for help. As the train roars through, Clay can only watch, frozen in terror as his girlfriend disappears under the stoned track. Tearful for the horrific sight that he has just witnessed, he has a brief glance at the button he is still holding in his hand before returning his attention back to the spot where Christine was dragged to her death.