Mae remarks that now that Big Daddy has gone to bed, the family can talk. Everyone but Brick is present. Mama marvels about how much Daddy put away at dinner. Gooper remarks with grim relish that he hopes he does not have to pay for it later.
Mama asks for Brick and Gooper replies that he is drinking. Mama rebels saying that people just drink. Maggie moves to fetch him, leaving an awkward silence in the room, and Mama burps. When Gooper begins to tell Mama, Mae pokes him in the side and circles the room like a burlesque ballerina, commenting on the breeze. She muses abruptly that she fears Brick told Daddy something he shouldn't have. Gooper starts again, and Mae stops him, moving to give Mama a kiss.
Mama pushes her off. Unaware that Brick has entered behind her, she muses about Brick: he is just broken up about Skipper's death. Calm as before, Brick moves to freshen his drink. Mama turns to him and sobs in anguish: "I just cain't staiiiiiiii-nnnnnd—it" The family surrounds Mama, urging her to stay calm. She cannot as the family members are staring at her as if "big drops of blood" had broken out on her face. They begin to tell her. With a terrified dignity, and Williams noting that, "she almost stops being fat," Mama demands to know everything. Brick sings to himself from the doorway, and moves out onto the gallery. Mama repudiates the family and calls for Brick, her "only son." She wants Brick to tell her.
Gooper protests, and Mama rejoins that he never liked Daddy. Gooper insists that, as the sick get sly about their pain, Daddy should be put on morphine. Doctor Baugh has left some, and Mae can administer the needle. Mama reproaches Gooper for wanting to see his father dead. She implores Maggie to help straighten Brick out so he can take over the place. Mae and Gooper protest angrily, saying that Brick can carry nothing but footballs and highballs. Maggie has never seen such malice and she accuses them of vilifying Brick out of avarice and greed. She and Mama embrace.
Gooper confesses that he has always resented Daddy's love for Brick. But now poisons are destroying him, and he wants his share of the estate. Brick enters, to Gooper and Mae's derision, singing to himself. His smile has grown more vague and brighter, and he prepares another drink.
Gooper and Mae present Mama with a drafted will. Mama rejects it with disgust. Speaking in Daddy's language, Mamma denounces it as crap. She awkwardly embraces the distant Brick, murmuring that he looks just as he did as a boy. Gooper is livid with sibling envy. Maggie assures Mama that Brick hears her. Mama declares that they have got to love each other and stay together. Daddy's dream is that Brick provide him with a son before he dies, a "grandson as much like his son as his son is like Big Daddy."
Act IV begins with the revelation of Daddy's cancer, a revelation that immediately splits the family into its respective camps. The "good" children, that is, the successful Gooper and fertile Mae, reveal themselves in their avarice, envy, and greed. Speaking in Big Daddy's name, Mama identifies Brick and Maggie as his rightful heirs.
The scene begins in dramatic irony, Mama still unaware of her husband's cancer. Especially poignant is how Mama marvels at how much Daddy ate at dinner. Note how Gooper looks to Daddy's certain suffering with "grim relish." When Gooper and the doctor begin to tell Mama, Mae, as always, performs a burlesque of the dutiful daughter-in-law. Her eagerness for the revelation is clear nevertheless. Mama pushes her aside.
The revelation of Daddy's cancer to Mama is the principle action of this scene. As noted above, Mama appears as a comic and touching figure, a naïve, sincere woman who does her femininity wrong in her tragically bad taste and notoriously crude manners. Devoted to a husband who has no interest in her, Mama is a woman who above all has stood by her man. The play is enamored and at the same time somewhat amused with this image of dogged feminine loyalty. The revelation of Daddy's cancer is Mama's dignified moment.
Read more about Mama’s moment of dignity.
Upon the revelation, Mama reveals her investments immediately, calling for her only son and begging Maggie to help him get on his feet so he can take over the estate. Gooper and Mae spring into action, appearing at their most vicious, presenting themselves as the family's rightful heirs. Their sadism reveals itself. Gooper savors Daddy's suffering, wanting him drugged up and dead. He has always resented his parents' love for Brick and has moved to protect his interests. They present Mama with a will that she firmly rejects. As Gooper has warned, however, he knows how to protect his interests.
Oblivious to Gooper, Mama flings herself awkwardly against the indifferent Brick, his coolness forcing another woman into helpless desire. Though she knows all too well what has been going on, Mama places all hopes in Brick, in his assumption of his duties as Daddy's rightful heir. Brick must become a family man: he must provide Big Daddy with a "grandson as much like his son as his son is like Big Daddy." We have already remarked upon the narcissism of Big Daddy's dream. Though not explicitly observed, it is clear that the perpetuation of the family line through Brick is Daddy's immortality.
Brick turns from Mama, unable to comfort her, leaving Maggie to assure her that he recognizes her plea. He appears utterly removed from the travesty before him, singing to himself softly, moving in and out of the room, turning the phonograph and drowning the others out, progressively withdrawing into his drunken haze. Brick's "almost deadness" makes it impossible for him to fulfill his filial duties and assume his place in the family line.