Plot summary

In New York City on a cold day in early January, actress Katie McGovern (Mary Steenburgen) goes on an audition where she impresses Mr. Murray (Roddy McDowall), the casting director. Murray takes Katie out to eat at a local restaurant, explaining that the lead actress on a film, Julie Rose, walked off the set a week ago after many arguments with the director. The movie is currently shooting scenes in Canada which do not involve Julie, but they fear she will not return to complete her role. They are looking for an actress who looks similar to Julie to take over and Katie fits the bill. Murray offers to pay Katie $3,000 to go upstate and videotape an audition scene which will be sent to the director. If he likes what he sees, she will be cast and paid an additional $9,000.Although her husband, photographer Rob Sweeney (William Russ), is skeptical about the idea, Katie packs her bags for the overnight trip. Murray drives Katie upstate to the estate of Dr. Joseph Lewis (Jan Rubes), a psychiatrist who is also the film's producer. Lewis, who uses a motorized wheelchair, is pleased with Katie, gives her a script to study, and says they will tape the audition in the morning. Lewis reports he just got word that Julie Rose had a nervous breakdown and definitely will not be returning.The next day as a winter snowstorm begins, Murray and Lewis cut and dye Katie's hair to match Julie's, then videotape the audition. As the winter storm has gotten worse, Murray, who is Dr. Lewis' personal assistant, says the car will not start and the phone lines are down. However, that night, Murray starts the car easily and drives into town where he drops the videotape in the mail slot of a house. Evelyn, the woman living there, watches the tape, which also includes a taped message from Dr. Lewis, saying that this should be proof the Julie Rose is alive and they will contact her soon.Meanwhile in New York City, Rob Sweeney telephones the number Katie gave him, but finds it is out of service. When Rob contacts the operator, she informs him that the area code Katie gave him does not exist.Trapped at the mansion due to the fierce storm, Lewis and Murray try to make Katie feel at home, but she discovers her driver's license, bank cards and identification are all missing from her wallet. When she tries to make a phone call, she discovers the cord has been cut. Panicking, she rushes outside without a coat, but falls in the woods and Murray brings her back inside.When Katie confronts them about the missing identification and cut phone cord, Lewis denies everything and promises to have Murray take her back to the city in the morning. Nonetheless, Katie puts furniture against the door to her bedroom to keep them out before going to sleep, but during the night, Murray comes in through a secret passage behind a full-length mirror.When Katie wakes up the next morning, she finds that her ring finger on her right hand has been cut off. She discovers the passageway behind the mirror and goes to the attic where she finds a working telephone. She phones her husband, Rob, screaming that they are going to kill her. Rob says he is coming to get her, but she is too upset to give him coherent directions. Nonetheless, Rob and Katie's brother, Roland (Mark Malone), drive upstate trying to track her down from the rambling things she said.Meanwhile, Katie finds Julie Rose's dead body in the attic and is stunned by how much alike they look. However, Murray catches Katie before she can telephone the police. Dr. Lewis explains that they are blackmailing Julie's identical twin sister, Evelyn. Lewis says that Evelyn married for money, but later committed murder to keep the money. Julie witnessed the murder and came to Dr. Lewis as a psychiatric patient. Lewis suggested they blackmail Evelyn. However, Evelyn had Julie murdered and had the killer cut off Julie's ring finger as proof of her death. Mr. Murray found Julie's dead body and brought it back to the house.They start to sedate Katie, but two policemen come to the door. Katie tells police they are trying to kill her, but Lewis says that she is one of his delusional patients. Katie convinces police to go to the attic, but they do not find Julie's body. After they leave, the two sedate Katie and Murray takes her upstairs where she finds Julie's body in her bed.A little later when Katie awakens, she overhears Evelyn and Dr. Lewis negotiating for the blackmail money. Katie pretends to climb out the window and run away, but while Murray and Lewis go outside after her, she comes downstairs, pretending to be Julie, and confronts Evelyn. However, the ruse does not fool Evelyn who tries to stab her with a letter opener, but Katie fends her off and kills her, stuffing her body in the window seat. Meanwhile, Rob and Roland arrive in the small town and go to police for help.When Mr. Murray and Dr. Lewis come back inside, they find Evelyn going upstairs. Murray accompanies her, but he quickly realizes she is Katie, not Evelyn. Katie stabs Murray in the neck, killing him. Pretending to be Evelyn, Katie comes downstairs and tries to leave, but Lewis realizes she is not Evelyn. Katie rushes back upstairs. Lewis pulls himself out of his wheelchair and follows her using a cane. Lewis goes to the attic, finds Julie's dead body, and stabs it, believing it is Katie. However, coming from behind, Katie stabs him in the back. He lunges at her, but steps on a bear trap she set. With his leg ensnared and a knife in his back, Lewis collapses and dies.A little later, Rob and Roland arrive at the mansion and rush to the attic. A traumatized Katie can barely talk, but Rob hugs her tightly.