While recuperating from an injury he received in the South Pacific, U.S. Marine Sergeant Johnny Meadows corresponds with Rosemary Blake, a woman he has never met, and whose name he found inscribed in a book. Johnny dreams of the day when he will finally meet the woman who has been sending him love letters from Monteflores, California. Soon after he returns to the United States, Johnny boards a train for Monteflores, and, en route, meets Dr. Leslie Ross, who has just taken a job as the town's physician. As Leslie and Johnny become acquainted, their train derails and many of their fellow passengers are injured. After helping Leslie attend to the injured passengers, Johnny goes to the Blake mansion expecting to meet his sweetheart. When Johnny arrives, however, he is greeted by Hilda, an elderly woman who introduces herself as Rosemary's mother. Delusional and crippled, Hilda tells Johnny that Rosemary is absent and will not be home for a few days. While Johnny settles into the Blake mansion and awaits Rosemary's return, Ivy Miller, Hilda's housekeeper, visits Leslie in a very agitated state. When Ivy disappears from her office soon after, Leslie suspects that she meant to tell her something important about Hilda. As the days pass, Johnny begins to wonder why Hilda is not telling him when her daughter will be returning, and admits his concern to Leslie. One day, Hilda follows Johnny to Leslie's office, and overhears Johnny tell the doctor that he is in love with her. Believing that Leslie is deliberately interfering with her plans, Hilda sets out to ruin the doctor's reputation. Johnny later tries to learn more about Rosemary by visiting the artist who painted her portrait in San Francisco. Ivy, meanwhile, writes a letter to Leslie warning her of Hilda's mental illness, but Hilda finds the letter, tears it up before it is mailed and kills Ivy. After learning that Hilda paid an artist $1,000 to paint a portrait of an imaginary girl, Johnny races back to Monteflores to expose Hilda's lie. Hilda confesses her deception, and tells Johnny and Leslie, who are now engaged, that she created an imaginary daughter to take the place of one she could never have. Hoping to prevent Leslie and Johnny from discovering Ivy's body, Hilda sabotages their car so that it will roll off a cliff and kill them. Hilda's scheme is foiled, however, when Johnny and Leslie discover the trap. To prove Hilda's guilt, Johnny and Leslie fake the sounds of a fall and wait for Hilda to telephone the police with an incriminating "accident" report. Realizing that she has been caught, Hilda turns to Rosemary's portrait for solace, but, at that moment, the heavy picture falls from the wall and kills her.