George Eastman (Montgomery Clift), the nephew of industrialist Charles Eastman (Herbert Heyes), takes a job in his factory to learn the business. While working there, he starts dating factory worker Alice "Al" Tripp (Shelley Winters), who becomes pregnant.
At the same time, he meets society girl Angela Vickers (Elizabeth Taylor), and loses interest in Al. Shortly after Al tries to blackmail George into marrying her by threatening to expose their relationship to Angela, she is killed in a boating accident, while out on the lake with George. The film ends when George is convicted of her murder.
The film opens with George Eastman being picked up while hitchhiking and then dropped off at the factory of an important businessman, his uncle, Charles Eastman. Mr. Eastman is not in the office so his staff phones him at home. Eastman invites George to drop out to the house at 7:00 p.m. Eastman intends to hire George to work in his factory. Suddenly, Angela Vickers, who was seen earlier driving past George in her white Cadillac convertible, comes in with her date, and George is obviously smitten with her, although she rushes out before he can even meet her.
The next day George is thoroughly instructed to "act like an Eastman" and not date any of the women who work at the company. He is given a tour, and the women are quite taken with him. He starts with menial work, and a worker, Alice "Al" Tripp, cannot take her eyes off him. George begins making suggestions to Mr. Eastman about ways to improve productivity in the mill. Later George goes to the movies alone and happens to sit near Al. He moves closer to her and engages her in conversation. After the film George walks with Al, and she briefs him on how Eastmans are brought up through the company. George walks Al home. He puts his arm around her; it appears that he is unconcerned with the anti-fraternization policy at work. The two seem to have an instant chemistry and kiss right away. Al warns George that he has to be careful.
The next day George and Al chat as they leave work and then go for a drink together. Al points out the culture clash, but George tells her he has only been to Mr. Eastman's home once; he is not living the high life. Al seems to warm up to George more and stops worrying about his high-class status. George takes her home, and because it is raining and he is driving a convertible car, he comes in the house despite Al's reservations about her strict landlady, and they begin to dance in the darkness. George does not leave until the morning.
The next day Mr. Eastman spots George in the factory and instructs his staff to promote him. Mr. Eastman also invites George to a party at his home. George attends the party, although Al is unhappy with it because it is his birthday, and she wants him with her. George finds himself ignored at the party and ends up playing pool alone. Angela happens in just as George is making a difficult trick shot. She asks him why he is all alone and seems to enjoy watching him play pool. Angela is a socialite and seems to appreciate that George knows it and reads about her in the newspaper. Mr. Eastman insists that George phone his mother, who works at a mission. The contrast between the poor mission and the affluent Eastman home is stark. Angela takes George dancing. Suddenly, George's relationship with Al seems lessened. Al expects George to try to come over early so they can celebrate his birthday together, but he ends up staying late with Angela. Al seems to sense that George has met someone new and specifically asks if he likes Angela; this prying troubles George. His new status as department head at the plant seems to put her off balance. Upset and crying, she reveals that she is pregnant.
George is seen seeming to stew over his options. He calls Al and tells her he is looking for a doctor. He finds one (Ian Wolfe) who refuses to help. What the movie implies, but does not explicitly state, is that the doctor is intended to procure for Al an abortion.
Angela invites George to spend Friday night together. George is melancholy. He is trying to decide if he wants to join Angela's world. Angela is at peace in George's arms. He is an outsider, different, deep and far away, mysterious and alluring. George tells Angela he loves her and has since the first time he saw her, maybe even before he met her. Angela tells George she loves him too. Angela plans the weekend at the lake and invites George to join her. She starts planning their future together. George tries to figure out how to handle both his pregnant girlfriend and a debutante.
Al and George decide they will marry when he gets his vacation, somewhere out of town where people will not know of it. But George is starting to think about life with Angela. George hears a radio report about the high incidence of death from car accidents and drownings. He starts to hatch a plan to relieve him of his burden. Angela pops in unexpectedly and picks George up, inviting him to spend his Labor Day vacation with her at her lakeside home. Angela insists he come so she can show him off to her family. George accompanies Angela to the lake, telling Al that he will be visiting his uncle there.
At the lake, Angela and George carry on their affair. A picture of the two ends up in the newspaper; Al sees it, and rushes to the bus station where she meets George in secret and demands he marry her immediately. George lies to Angela, telling her that his mother is sick, and leaves with Al. Unable to find anyone to officiate because of the holiday, George takes Al to the lake, where they rent a boat, and row out to a secluded area. Al tries to put a brave face on their relationship, while George struggles with his frustrations and implied thoughts of murder. They get into an argument with Al accusing George of wishing for her death after seeing a falling star; then Al stands up, George tries to restrain her, and in the struggle the boat capsizes into the water, with Al and George.
George pulls himself out of the lake, terrified. He encounters some campers, who point him back to his car where he is able to make his way back to Angela. Al's body is dragged from the lake, and suspicions are roused by the fact that the man who rented them the boat noticed their car, and it is has disappeared.
George tries to relax, going for a boat ride with Angela and some of her friends. There is, however, much talk of the drowning, and he is visibly shaken. Angela's father (Shepperd Strudwick) has a heart-to-heart with George, who tells him of his impoverished and hardworking background. George's honesty wins him over, and he approves of their relationship.
Meanwhile, investigators question Al's landlady, who tells them that George and Al were dating. When Angela and George return to her house from a drive there are police waiting. George makes his way on foot through the woods, but is caught by sheriffs, and given to district attorney Marlowe (Raymond Burr). Marlowe questions the Vickers family; Angela collapses in shock when she hears about what happened.
At the trial, a parade of witnesses seem to condemn George, including a coroner who testifies that Al was beaten before she drowned. He takes the stand, and testifies that he wanted to drown her but did not. Marlowe accuses George of lying, forcing him to reenact the event by bringing the boat into the courtroom. George is found guilty of committing the murder, and sentenced to death by electric chair. He comes to the understanding that by not saving Al as she was drowning, he was guilty of her murder. Angela comes to see him one last time and tells him she loves him. The movie ends as George is led off to the electric chair, dreaming of Angela as his cell-mates all give him a final farewell.