A fun-loving bachelor woos and weds a secretary, but the bonds of this marriage aren't strong enough to stop his philandering from continuing.

In early 1960s San Francisco, single, thirty-three-year-old Tillie Schlaine attends Burt and Gertrude Wilson's party for the express purpose of meeting Pete Seltzer. The encounter is awkward, with Tillie unsure how to respond to Pete's biting wit and lecherous approach. Later, Pete asks Tillie for a ride home and in the car reveals that he is a "motivational researcher" for new products. Amused by his banter, Tillie allows him to invite himself into her apartment, but once there she is rankled when he advises her not to wear a girdle or bra. Gertrude, however, soon after urges Tillie to call him on some pretense, and Tillie meekly assents, resulting in a date that evening. At her apartment, she tidies up in spite of herself, then accompanies Pete to dinner at a mediocre Greek restaurant, which Pete has chosen only in order to make a pun about the short waiter: "Beware Greeks wearing lifts." After a few desultory dates and a week without calling, Pete shows up at Tillie's door and invites her to a movie and dinner at a diner. She agrees to accompany him to his apartment afterward for sex, and although she is at first ill at ease, they enjoy their evening together. The relationship soon builds into a love affair, and when Tillie occasionally finds another woman's hairpins by the bed, she ignores them. One day, he announces that he has earned a promotion to an executive position, prompting Tillie to announce that it is time for them to marry. A few years later, they have a beautiful baby boy named Robbie and move into a handsome suburban home. Their home life is happy, but when Tillie stops by Pete's office one day, she spots him in the hallway fondling his secretary. When he comes home that night, she eventually confronts him about his infidelity, and when he defensively changes the subject, she declines to pursue the conversation. Another time, Lucy Lund, one of Pete's lovers, calls and asks to meet Tillie. At a restaurant, Tillie gently disillusions the younger woman by revealing that Pete has many lovers. That night, Pete makes love to a willing Tillie, and when Burt propositions her soon after, she demurs. Their genial domestic life is shattered, however, when one day Dr. Willett visits to inform them that nine-year-old Robbie has a fatal illness. Both Pete and Tillie respond with quiet devastation but determinedly hide the truth, and their grief, from Robbie. Hoping to "keep Robbie safe in a world of nonsense," Pete leads the boy in a series of pranks on their stuffy neighbor, Mr. Tucker, and takes the family on a fishing vacation, where Robbie is too soft-hearted to kill the fish. As the year progresses, Robbie's illness is in remission but Pete and Tillie know their time with him is limited. The couple's relationship grows strained under the pressure, causing Tillie to refuse Pete sex, and Pete to find solace in bourbon. One night, as Pete and Robbie listen to an Abbott and Costello record, Tillie steps outside to rail at God, calling him a "son of a bitch bloody butcher," finally breaking down in anguish and fury. That winter, Robbie dies. Tillie is stoic and, despite her and Pete's aversion to organized religion, they hold a church funeral service. Over the next six months, they live in seclusion, then are coaxed into attending a cocktail party. Pete flirts with a redhead, causing Tillie to ask him to take her home. At home, when Tillie states that she wants to be counseled by Father Keating and wonders if they are being punished, Pete lashes out that Robbie died for no reason. She retorts that he hides his feelings, to which Pete states that talking makes him feel worse. When she asks why he stays with her, Pete answers, "I'd rather not discuss things with you than with any other woman in the world." Later that night, Pete drunkenly mentions that they have not had sex in a year, and after Tillie replies that he should have an affair, Pete moves into an apartment in the city. Tillie begins doing charity work and strikes up a friendship with flamboyant homosexual Jimmy Twitchell. Jimmy makes a sport out of trying to discover Gertrude's true age, and to this end insists that Tillie bring Gertrude with her to the police station to register their charity lottery, knowing the police will ask her age. On the way to the police station, Tillie is annoyed when Gertrude flippantly offers the name of a divorce lawyer and suggests she sue on the basis of infidelity. Inside, when the policeman asks Gertrude her age, she is unable to answer and finally faints. As they leave she blames Tillie, and the two commence a fistfight that reaches a crescendo when Tillie inserts a water hose up Gertrude's dress and Gertrude places a garbage can over Tillie's head. Soon after, Tillie seeks refuge in a rest home. One day Jimmy visits and shocks her with a marriage proposal, offering food, shelter, companionship and a chic makeover. She gently rebuffs him, and later, just as she is readying to leave the sanitarium, Pete shows up. After asking why she did not call him, he declares that their separation is not working out. A ten-year-old boy runs by, followed by his exasperated mother, and both tear up. Pleased to see Pete show his emotions, Tillie tells him that she has never loved him more than this moment. "You have no faults at all," she summarizes, "you're just hopeless." Pete, who has already moved Tillie's bags into his car, leads her out of the sanitarium, his hand on her behind.