Aging widow Sara Goldfarb lives alone in a high-rise apartment building in the Brighton Beach neighborhood of Brooklyn, New York. One summer day her only child Harry, an aimless young man, visits her, steals her television set and pawns it to buy drugs. After Harry and his friend, Tyrone C. Love, "get high" on the drugs, they wander through the Coney Island amusement park, making plans to deal large quantities of heroin and use the profits to retire. In the days that follow, Sara buys back the television set, as she has done many times before, from pawnshop owner Mr. Rabinowitz, who suggests that Sara ask the police for help with her son. Sara refuses, explaining that Harry is all that she has. Back at home, while she watches her favorite game show "Tappy Tibbon's Month of Fury," Sara is offered a chance to appear on a television show by a phone solicitor. Longing for the days when her family was together, she immediately imagines herself on stage in the slim-fitting red dress she wore to Harry's high school graduation. When Sara discovers she is too plump to fit into the dress, her friend helps her start a strict diet and Sara becomes obsessed with all the foods that she is now forbidden to eat. Meanwhile, Harry and his girl friend, Marion Silver, discuss their future. Marion, who feels abandoned by her wealthy family, receives support and encouragement from Harry to open her own clothing design business. Days later, Sara is chatting with her older female friends on the sidewalk outside the high-rise, when the mailman delivers the television appearance application package. All of the women then excitedly help Sara fill out the application. Later at Tyrone's apartment, after he and Harry inject heroin, Harry fantasizes that he is walking alone to the end of a pier toward Marion, who turns to him smiling, filling him with joy. At the high-rise, Sara watches the game show, which promises to transform her life, if she would decide to remove red meat and refined sugar from her diet. When Sara's cravings become overwhelming, she gets a diet pill prescription from an unscrupulous physician and returns home, scoffing at the refrigerator, the symbol of her cravings. The pills make her frenetic, and as she cleans and rearranges her entire household, she begins to fidget and sweat profusely. Uptown one evening, Marion sees Arnold, her psychiatrist, to satisfy her parents' demands. On the street, Harry and Tyrone sell the heroin and use part of the huge profits to finance Marion's clothing business. Harry, happy that he might finally be on his way to a satisfying life, visits his mother and apologizes for his past behavior. At her apartment, he notices that Sara is gaunt and grinding her teeth, and asks if she is on drugs. Sara admits to taking diet pills, but, claiming that she has no reason to live without a husband or son to look after, refuses to give up the one thing that makes her feel good and helps her lose weight. Harry begs her to quit, knowing from experience how drugs can destroy her life, but she demurs. Late one night, while Tyrone is meeting some drug dealers to discuss increasing his job responsibilities, gun fire is exchanged and Tyrone is caught by the police. Harry bails Tyrone out of jail and reports that most of their money has been lost because of a drug war between Italians and Blacks. Drugs are in short supply and very expensive. The following fall, Marion and Harry, having become increasingly addicted to heroin, isolate themselves in Marion's apartment. They bicker over the last of their drug supply and at Harry's request, Marion has sex with Arnold to earn money for drugs. The betrayal ruins her relationship with Harry and emotionally devastates them. When a drug shipment finally arrives in town, Tyrone and Harry wait in line with hundreds of others at a convenience store loading dock. As the anxious crowd pushes towards the dealers, someone fires a shot and Harry returns to Marion without drugs. Frustrated by Marion's insatiable need for drugs, Harry gives her the telephone number of a pimp named Big Tim, who will provide heroin in exchange for her prostituting herself. Meanwhile, the effect of the diet pills is dwindling for Sara and she increases her dosage, causing her to hallucinate that she is actually on the game show. In her mind, the show's host appears in her apartment with the glamorous television version of Sara and they criticize and laugh at the real Sara along with the television audience. Suddenly the walls break apart, revealing that her entire apartment is a television set. Everyone then parades around her reclining chair, chanting "feed me Sara, feed me Sara." Sara, disheveled and unkept, flees the apartment and takes the subway to Malin and Block, the company that promised her a television appearance. There, she demands to know why they have not called her. The office personnel, certain that Sara is mentally ill, call the police, who take her to a psychiatric ward. Spurred by the possibility of obtaining drugs in Florida, Tyrone and Harry drive south, but when Harry begins to writhe in pain from an infection in his arm caused by injecting drugs, Tyrone takes him to a hospital and both are jailed for possession. In New York, Marion, desperate for heroin, prostitutes herself to Big Tim and returns to her apartment, numb and vomiting. She receives a call from Harry, who tearfully apologizes. When she blankly asks him to come home, he agrees, although they both know it is impossible to renew their relationship. In the psychiatric ward, Sara, completely incapable of communicating, fails to respond to the hospital attendants' attempts to force-feed her, and so the doctor orders electric shock treatment. Marion, emotionally dead from the drugs and her loss, returns to Big Tim, who pimps Marion and another girl to a group of businessmen, who viciously encourage the young women's depravity. She returns home, cradling the package of drugs she received in her arms. Somewhere in the South, Tyrone serves his time in jail doing grueling day labor and lulling himself to sleep each night with images of his mother's comfort. Harry is finally taken to a hospital by prison authorities and his arm is amputated. When he wakes up from his surgery, he hallucinates that he is running toward Marion, who is standing at the end of the pier, but she disappears before he can reach the end. As he backs up, he plummets from the top of the building seen in his dream. On her bed in the ward, Sara lies brain dead from the treatments and falls asleep smiling, her head filled with fantasies of Harry and her husband together with her on television.