Brick is taking a shower in the bedroom he shares with his wife, Maggie. While undressing, Maggie complains that his brother Gooper and wife Mae have been having their monstrous children perform for Big Daddy, incessantly reminding him of their own childlessness. Now that Daddy is dying of cancer, Mae and Gooper are trying to cut them out of the estate. The doctors have lied to Daddy and Mama, claiming that Daddy only suffers from a spastic colon, but tonight the truth will be revealed.
Brick is not helping any with his incessant drinking and much-publicized stunt on the high school athletic field. Brick broke his ankle jumping hurdles. Maggie is confident of their advantage, because Big Daddy dotes on Brick, abhors Gooper and his wife, and has a "lech" for Maggie herself. Suddenly Maggie catches sight of Brick staring at her in the mirror. She cries that she knows she has become hard and frantic. Living with someone who does not love her has made her a "cat on a hot tin roof."
Fiercely Maggie locks the door and draws the curtains. As she attempts to seduce him, Brick warns her against making a fool of herself. Maggie murmurs she has realized her mistake: she should not have confessed to making love with Skipper.
Maggie continues and says that Brick and Skipper's love was sad and awful because it could never be satisfied or even talked about. Maggie recalls how on their double dates in college it always seemed the boys were out together. The night of the Thanksgiving game, Maggie confronted Skipper on his desire. He made a pitiful attempt to prove her wrong.
Threatening to kill her, Brick hurls his crutch at her. Maggie insists that now is her time of the month to conceive and they must make love. Brick wonders how she plans to have a child by a man who cannot stand her. Big Daddy enters ferociously and greets Brick. The servants enter with Daddy's cake, and a grotesque sing-a-long commences. Daddy furiously orders everyone to stop. Mama sobs that he has never believed that she loved him. "Wouldn't it be funny if that was true" Daddy murmurs.
Daddy bellows for Brick. Maggie delivers him, giving him a kiss on the mouth that he immediately wipes off. Daddy asks Brick why he wiped off her kiss. Mae and Gooper have been saying that he won't sleep with Maggie. As Brick freshens his drink, Daddy asks him about his drinking problem. Brick cannot explain.
Drawing Brick close, Daddy recalls his world tour with Mama. He anxiously closes the doors and asks if Brick has ever been terrified of anything. He aims to cut loose and get himself a woman. Brick explains that he has not gotten the click in his head that makes him peaceful, and he attempts to flee his father. Daddy makes Brick a deal: he will give him a drink if he tells him why he drinks. Daddy knows that Brick is lying since he started drinking when Skipper died. Daddy asks if there was something "abnormal" in their friendship.
Daddy replies that having just come from "death's country," he is not easily shocked. Brick insists that his friendship with Skipper was clean and true until Maggie got the idea Daddy is talking about. Upon his back injury, she put the idea into Skipper's head, and he became a lush and died. Daddy knows he is not telling the full story and Brick says that Skipper made a drunken confession to him over the phone, and Brick hung up on him. Brick's disgust with mendacity is disgust with himself. Daddy curses the "lying dying liars" around him and goes to bed.
Mae appears, and the family soon follows. Now that Daddy has gone to bed, they can finally talk. The family surrounds Mama and begins to tell her of Daddy's cancer. Mama calls for Brick, her "only son." She implores Maggie to help straighten Brick out so he can take over the place. Gooper protests and says he has always resented Daddy's love for Brick. Gooper and Mae present Mama with a drafted will and Mama rejects it in disgust.
Mama embraces the distant Brick, begging him to provide Big Daddy with a grandson before he dies. Suddenly Maggie announces that she and Brick are to have a child. Sobbing, Mama flees jubilantly to tell Big Daddy. Mae accuses Maggie of lying. Maggie thanks Brick for saving her face. Brick puts down three shots, finds his click, and exits indifferently. Maggie forlornly gathers Brick's liquor bottles and locks them away, refusing to release it until he has sated her. Desperately she declares her love for him. The distant Brick can only reply: "Wouldn't it be funny if that was true?"