A woman is unhappy in her marriage to a boring, stiff judge, so she takes up with a wild-living RAF pilot, who ends up being more than she can handle.

One morning in a shabby London rooming house, landlady Mrs. Elton and neighbors Dawn Maxwell and Ken Thompson notice the smell of gas coming from the apartment of Hester and Freddie Page. Mrs. Elton uses her passkey to open the apartment and the trio discovers Hester lying unconscious near the gas fireplace. They also find a bottle of sleeping tablets and send for upstairs neighbor Miller, a disgraced doctor who is now a bookie. Miller revives Hester, whose suicide attempt has failed because she did not put enough money in the gas meter and the gas ran out. While Miller is tending to Hester, the nosy Dawn questions Mrs. Elton, who grudgingly reveals that Hester is not married to Freddie, who is away golfing. Hester's real husband is a prominent, upper-class judge, Sir William Collyer, and Dawn, eager to snoop further, calls Sir William and tells him that Hester has had an accident. When Hester is feeling better, she denies that she attempted suicide, but asks Mrs. Elton not to tell Freddie what happened, nor to admit Bill if he arrives. Mrs. Elton questions Hester about her actions, and Hester vaguely replies that when one is "between the devil and the deep blue sea," sometimes the sea looks inviting. While Hester is standing in the stairwell, Bill arrives, and Hester is forced to talk to him. The kindly Bill, who still loves Hester even though she abandoned him for the much-younger Freddie, discovers that Hester and Freddie are desperately poor. Hester explains that Freddie, who was an RAF pilot during World War II, no longer works as a test pilot, and they rely on his gambling and her paintings for income. Hester refuses any help from Bill, however, and maintains that she still loves Freddie. Bill offers to take Hester to tea that afternoon, then leaves, and while he is being driven to the courthouse, remembers the argument that he and Hester had ten months earlier: In Bill's chambers, Hester tells him that she will be leaving him that night to accompany Freddie to Canada, where he has obtained a job as a test pilot. Bill pleads with Hester not to destroy their fifteen-year marriage, but she insists that she has been in love with Freddie for months. Bill is called into court before they can finish, and while he is on the bench, he receives a note from Hester stating that she is leaving. Back at the rooming house, Freddie arrives home unexepectedly, and realizes that he had forgotten Hester's birthday, which was the day before. Freddie comforts the crying Hester, and later, discusses with her a job interview he has that afternoon. As Hester is preparing to accompany him, Freddie accidentally finds the suicide note she had left for him but later retrieved and put in the pocket of her dressing gown. Astonished, Freddie leaves without saying anything or revealing what he has found. At the neighborhood bar, Freddie calls his Canadian friend, Jackie Jackson, and begs him to come over. As Freddie is waiting for Jackie, he remembers the first time he saw Hester: At a country club, Freddie meets Bill on the golf course, and later, meets Hester in the bar. Although he admires her beauty, Freddie tells a friend that he never pursues married women. Soon after, however, Freddie arranges to meet Hester while she is away skiing with friends, and Hester becomes attracted to the lower-class but charming young man. The couple embarks on an affair, and after several months, Freddie is offered a ten-week job in Canada. Hester declares that she cannot bear to be separated from him, and so Freddie agrees that she should leave Bill and go with him. Back at the bar, Jackie arrives and Freddie reads him Hester's note, in which she states that he will never be able to feel for her what she feels for him. Hester walks in as Freddie is reading, and Jackie quickly leaves. After Freddie staggers home, he bumps into Miller and complains about feeling like a murderer because of Hester's actions. Freddie then caustically tosses a shilling on the table for Hester to put into the gas meter if she wants to attempt suicide again. After Freddie passes out, Hester meets Bill for tea and he tells her that it is not too late for her to return to their marriage. Hester refuses, and at home, is upset that Freddie, who promised her that he would never fly again, is going to seek another test pilot job rather than a management position. Freddie struggles to tell Hester that he loves her as much as he can love anyone, even if it is not enough for her, but that he cannot go on living with her if he is driving her to suicide. Hester cries hysterically when Freddie states that he is leaving her immediately, and collapses in tears after he departs. That evening, as Hester desperately hopes for word from Freddie, Miller advises her to forget him. Instead, Hester begins a frantic search of London clubs, but just misses Freddie and Jackie several times. Bill, alerted by a letter from Freddie that he has left Hester, finds the weary Hester and takes her to their former home, where he still lives. Hester again states that she cannot return to him, even though he asserts that he loves her more than ever. Hester returns to her flat, where Jackie is packing Freddie's clothes. When Freddie calls, Hester begs him to pick up his things himself, assuring him that she only wants to see him one more time, but Freddie refuses. After Jackie leaves, Hester puts Freddie's shilling in the gas meter and is about to attempt suicide again when she is interrupted by Miller, who saw her blocking her doorway with a rug. Miller calmly states that she must face the fact that Freddie needs her more than she needs him, and that if they are both to be saved, it is up to her to end the relationship. Miller's prediction that Freddie will return then proves accurate, but as Freddie makes small talk, hoping that Hester will persuade him to stay, Hester realizes that she must have the courage to let him go. Hester quietly bids Freddie farewell and, after he leaves, stands in the middle of her lonely apartment, staring at the closed door.