In 1969 Pasadena, California, a couple seeks the aid of the medium Shaun San Dena (Flor de Maria Chahua) saying their son (Shiloh Selassie) has been hearing evil spirits' voices after stealing a silver necklace from gypsies. San Dena aids the family by carrying out a seance, but they are attacked by an unseen force that pulls the boy into Hell. The medium says she will encounter the force again one day.
In present-day Los Angeles, bank loan officer Christine Brown hopes to be promoted to assistant manager over her co-worker Stu Rubin. Her boss, Jim Jacks, advises her to demonstrate that she can make tough decisions to get a promotion. Christine is visited by an elderly gypsy woman, Sylvia Ganush, who asks for an extension on her mortgage payment. Though empathetic with the old woman's crisis, Christine denies Ganush an extension to prove herself to her boss. Ganush begs Christine not to repossess her house and kneels in front of her. Christine gets scared of the woman's bizarre pleading as she is helping her to stand up and calls security, who take Ganush away while Ganush blames Christine for "shaming" her and vows to take revenge. Jim compliments Christine on how she handled the situation.
When Christine goes to the bank parking garage to drive home, Ganush attacks Christine in her car, rips a button off Christine's coat and uses it to place a curse on Christine. Later, Christine and her boyfriend Clay Dalton meet the fortune teller, Rham Jas who tells Christine that she is being haunted by an evil spirit. At home, Christine is attacked by the spirit and has nightmares about Ganush. At work the next day, Christine snaps at Stu and has a projectile nose bleed that soaks her boss in blood. She runs away and Stu secretly takes a file off Christine's desk.
Christine goes to talk to Ganush but learns that she died the previous night after visiting her house. Christine returns to Rham Jas, who explains that as long as Christine is the owner of an accursed object, she will be haunted by a powerful demon called the Lamia (loosely based on the Greek child-eating demon) that will torment her for three days before taking her to Hell for eternity. He suggests a sacrifice to appease the demon. Desperate to stop the attacks, Christine reluctantly sacrifices her pet kitten. At a dinner party with Clay and his parents, she is again tormented by the Lamia, but this time through the use of illusions, which frightens the Daltons.
Christine returns to Rham Jas who says that Shaun San Dena will risk her life to stop the demon for a fee of $10,000. San Dena prepares a seance to trap the Lamia's spirit in a goat and kill it, and then allows the Lamia to inhabit her body. Rham Jas tries to persuade it not to steal Christine's soul, but it vows never to stop until Christine dies. Christine then places San Dena's hand on the goat, causing the spirit to enter its body. San Dena's assistant, Milos, attempts to kill the goat, but is bitten by the goat and becomes possessed, attacking the members of the seance. San Dena banishes the Lamia from the seance, but dies in the process. Christine thinks the medium has overcome the Lamia, but Rham Jas explains that she only managed to drive the spirit away until the next day. Then he seals the cursed button in an envelope and tells Christine that she can get rid of the curse by giving the button to someone as a gift, thereby passing the curse on to that person.
Christine decides to give the envelope to Stu in revenge for his stealing her work, but changes her mind after seeing how pathetic, tearful and panicky Stu is when he meets her. With guidance from Rham Jas, Christine learns that she can give it to Ganush even though she is dead. Christine digs up Ganush's grave and jams the envelope in her mouth just in time before dawn.
Christine returns home and prepares to meet Clay at Los Angeles Union Station for a weekend trip to Santa Barbara. She gets a message from her boss telling her that she landed her dream position after Stu confessed to stealing her work and was fired. At the station, Christine also buys a coat that she has been wanting as a sign of a new beginning. Clay, planning to propose, reveals to Christine that he found the envelope containing the cursed button in his car. Christine then realizes she mixed up her envelope with another that she gave to Clay when she accidentally dropped it. Horrified, Christine backs away and falls onto the tracks. As a train barrels towards her, fiery hands suddenly emerge from the tracks and drag Christine into the neverending flames of Hell, as a horrified Clay watches from the platform above with the cursed button still in his hands.

Question: What will happen if Christine gives the envelope with the button in it to someone?
Answer: The curse will pass to them
Alternative answer: The curse will be passed on.