An ambitious beauty marries a vintner, then falls for one of his workers.

From her jail cell, Phyllis Hochen recounts how she almost executed the perfect crime: One night in Napa Valley, California, Phyllis, who is married to vineyard owner Paul Hochen, disdainfully responds to her mother-in-law Emma's fear of prowlers by shooting a gun to scare them off. Still fearful, Emma calls the sheriff, and after Phyllis hears her young son Michael stirring, she warns them both to return to bed. What Emma has actually heard is the arrival of Phyllis's new lover, rodeo star San Sanford, who hides in the kitchen as Deputy Watkins and Paul's brother, Rev. Stephen Hochen, arrive. Stephen, who remains suspicious of the seductive Phyllis despite her assurances that Emma was merely imagining noises, advises her to ignore Paul's well-known practice of keeping his doors unlocked. The next morning, Paul shows wine merchant Ezra Benton around the winery, explaining that the business has been handed down through generations of Hochens. During lunch, Gino Verdugo, Paul's best friend and grape supplier, quietly informs Paul that a Fresno businessman has offered to buy his grapes, infuriating Paul, who believes that the sale will ruin the grape market. Watching Paul, an irritable Phyllis remembers how they met: Phyllis and her friend Gwen are flashy party girls in Los Angeles when Paul and Gino offer to buy them dinner. While Paul and Phyllis dance, she explains that she moved from London with an Air Force sergeant who has since disappeared. When Paul hears that Phyllis has a six-year-old son named Michael, he takes them all to the beach the next day, and after Michael sees Paul kiss Phyllis and becomes upset, Paul hugs the boy and gives him a seashell, explaining that it carries the sound of the sea to ward off loneliness. After their weekend, Phyllis is surprised that Paul still wants to see her, and although she tries to reveal her sordid past and her inability to love her son, Paul proposes, insisting that she is like a vineyard that has not been tended to properly. Coming out of her reverie, Phyllis, hoping to break her tie to San, tells Paul that she is sending Michael back to boarding school and wants to go on a vacation, but he explains that he cannot leave his business. Paul then informs a forlorn Michael that he can stay, and although the boy begins to reveal what he saw the previous night, Phyllis interrupts them. Later, they attend the annual vineyard fair, where Gino reveals to Paul that he plans to sell out to the Fresno buyer, prompting Paul to punch him. A crowd gathers and the men are separated, after which Paul berates himself for his temper. Mistaking Phyllis' apathy for kindhearted tolerance, Paul agrees to her suggestion that he apologize to Gino before going home. She then rushes to the estate to meet San, who is growing impatient with her lack of availability. Hoping to run away with San, Phyllis plans to shoot Paul when he comes in the front door, but when Gino arrives, she kills him accidentally. Paul enters soon after and, believing Phyllis' story that she thought Gino was a prowler, prepares to call the sheriff. Knowing that San will leave her if she does not have the Hochen money and name, Phyllis decides to pin the murder on Paul. To that end, she lies to him that she is breaking parole and will be imprisoned and deported if questioned. As she has planned, Paul offers to take the blame, and they race to make it look as if Gino burst into a locked home and Paul mistook him for a burglar. In secret, however, Phyllis slips a note into the dead man's pocket that asks him to meet her at the house and mentions Paul's terrible temper. The police accept Paul's story about the break-in until they discover the note, after which he is arrested. Although Paul is indicted for murder, Stephen later tells Phyllis that the sheriff plans to acquit him at the trial. While her husband is in jail, she sends Michael back to school and carries out her secret tryst with San, who plans to leave town soon. Desperate, she tells him that Paul killed Gino in a jealous rage, and begs him to wait until the trial. To prevent Paul's acquittal, Phyllis takes the stand on the final day of the trial and claims that she killed Gino. When she is on the witness stand, however, she purposely makes vague, unconvincing statements, and as she has planned, the prosecutor makes it look as if she is protecting her husband. Paul is sentenced to death, and although he agrees with Stephen that Phyllis had ulterior motives, he confesses that he took the blame in order to protect his beloved Michael, adding that a war wound prevents him from having children of his own. Meanwhile, in the wine cellar of the estate, Phyllis brags about her scheme to San, and when Emma overhears, she suffers a simultaneous heart attack and stroke. With only hours left until Paul's execution, Stephen tricks Phyllis into admitting that she is not on parole. While the doctor orders Phyllis to administer strong medication to Emma every four hours, Stephen asks Paul's judge to reconsider the case, but is told that he must uncover new evidence. Stephen visits Emma and discerns from the movements of her fingers that she heard Phyllis say she killed Gino. Phyllis interrupts him, and while they quarrel, Emma manages to swallow two of her pills. When Phyllis gives her the scheduled pill, Emma dies of an overdose, and Phyllis is accused of murder. Stephen calls the sheriff, judge and lawyer, and although Phyllis begs them to believe she is innocent, she is jailed and Paul is freed. In the present, Phyllis finishes telling her tale to Stephen, and asks only for last rites before her execution. As she is led to the electric chair, Paul shows Michael around the vineyard that will one day be his.