When Jo Morris' marriage turned sour and heartless, she found sympathy and companionship with widower Larry Ellis. After Jo's husband is accidentally killed in a struggle over a gun with Larry, the adulterous couple find themselves on trial for their lives, with their lawyers fighting the pair's reluctance to turn against each other.

When Victor Santini, an undistinguished attorney, is approached by Mrs. Annie Brown to defend her daughter, Jo Morris, against the charge of murdering her husband, he demurs because Mrs. Brown lacks the money to launch an effective defense. Mrs. Brown's fervor finally convinces Santini to take the case, and he agrees to meet with Jo. In their interview, Jo recounts the events leading up to her husband Mike's death: One night, Mike, an abusive, drunk, threatens their little daughter Avis before leaving for work as a police detective. Jo has sought refuge from her loveless marriage in the arms of widowed accountant Larry Ellis, but has broken off their relationship out of guilt. When Mrs. Brown learns that Larry has asked Jo to leave Mike and marry him, she urges her daughter to reconcile with her lover. Jo then phones Larry and, upon discovering that his beloved young son was killed in an automobile accident, hurries to his side to console him. Soon after, Mike arranges for Lauber, an insurance agent, to come to the house to discuss a new life insurance policy. There, Mike maliciously tells Lauber that Jo wants him to take out a large chunk of insurance, but after Lauber leaves, Mike admits that he is going deaf and fears losing his job as a police officer. One day, while Larry is out of town on business, his domineering mother visits Jo and threatens to expose her "sordid affair" to her husband unless she stops seeing Larry. Upset, Jo phones Larry, who is in Sacramento working on the accounts of his old friend Morrie Goetz, and tells him of his mother's threat. Larry immediately flies to Los Angeles to comfort Jo, arriving at her house late that night. Overhearing whispering in the kitchen, the drunken Mike bursts in, pistol in hand, and fires at Larry. Larry struggles with Mike in self-defense, and the weapon goes off, killing Mike. When Jo concludes her story, Santini voices doubts because she initially lied to the police that Mike was killed by a prowler. It was only after Larry's cufflink was found on the kitchen floor that the police traced him to Sacramento, after which Larry lied that he had been confined to his bed, sick, at the time of the murder. Santini is mystified why the lovers seem to be protecting each other rather than themselves. At the trial, Phil Stanley, the cruel, condescending prosecuting attorney, calls Lauber to the stand and makes it seem as though Jo was eager to claim Mike's insurance policy. Under cross-examination, however, Santini gets Lauber to admit that Jo was not the least bit interested in her husband's insurance. Stanley next questions Goetz about Larry's obvious lie that he was in Sacramento on the night of the murder. Santini then counters that Larry was only trying to hide the trip from his domineering mother, and was not attempting to establish an alibi for murder. After Stanley calls Jo's character into question, Santini asks her to take the stand where, after testifying about the abusive nature of her husband, she admits that she had only one sexual encounter with Larry throughout their entire relationship. On cross-examination, Stanley tries to paint Jo as an adulterous, money-hungry wife, causing her to break down in tears. The next day, Larry is called to testify, and Stanley accuses him of premeditated murder and suggests that he flew back to Sacramento on the night of the murder solely to establish an alibi. After court recesses for the weekend, Santini, concerned about Jo's defense, confers with Judge Carey, the elderly, ineffectual attorney hired by Mrs. Ellis to defend her son. Santini asks Carey's cooperation in depicting Mrs. Ellis as a hateful woman who could drive her son to lie in order to hide his trip to Los Angeles. The next day, Santini calls Mrs. Ellis to the stand and then establishes the pattern of control that she exercised in every aspect of Larry's life, from his education to the path of his career and even the choice of his first wife. Santini then discloses that Mrs. Ellis hired a private detective to spy on her son and then threatened to fly to Sacramento to intimidate him into giving up Jo. In his summation, Santini makes an eloquent plea on Jo's behalf, while Stanley argues that this was clearly a case of premeditated murder. As they tensely await the verdict, Larry finally screws up the courage to stand up to his mother, who retaliates by calling him a murderer. After the jury judges them both innocent, Larry and Jo join hands and leave the courtroom together.