Tod Hackett has been recruited from Yale School of Fine Arts to work as a set and costume designer for National Films in Hollywood. When the novel opens, Tod has been in Hollywood for only three months and still marvels at the people and architecture of the city, both of which involve blatant and constant artifice and masquerading. Tod is most interested in the section of the population that does not seem to be masquerading—the imported, lower middle-class Midwestern immigrants who stand around the city and stare at the masqueraders. In his head, Tod has labeled these people the ones who "have come to California to die" and has decided to paint them in his upcoming masterpiece, an apocalyptic scene he has titled "The Burning of Los Angeles."
In his short time in Los Angeles, Tod has acquired an odd assortment of friends, including Abe Kusich, a belligerent dwarf bookie; Faye Greener, an untalented extra who wants to be a film star; and her father, Harry Greener, a former vaudeville clown who never found work in Hollywood but keeps up his clown act all day, even though his only job now is selling homemade silver polish door-to-door. Abe helped Tod find his current apartment, which Tod only decided to take upon seeing Faye Greener, who lives downstairs. Tod desires Faye, but she has unsentimentally told him that they must remain polite friends, as Tod has no money and is not particularly good-looking. Tod hopes that his chances with Faye have improved now that Faye's father Harry has fallen ill and Tod visits with the man nightly.
Harry fell ill at the house of Homer Simpson, to whom he was trying to sell silver polish. Homer has recently moved to Hollywood from Iowa on doctor's orders after a bout with pneumonia. Homer is not working, living on money he has saved and trying to forget the uncomfortable memory of his first and only near- sexual encounter, which occurred with a female tenant at the Iowa hotel where he once worked as a bookkeeper. Ignoring his instinct not to make himself vulnerable to excitement, Homer begins courting Faye. Tod, sensing that Homer is somewhat like the type of people he wants to paint in "The Burning of Los Angeles," befriends Homer out of curiosity.
Homer and Tod are not Faye's only admirers; Tod accompanies Faye out to a campsite in the hills where her sometime-boyfriend Earle and his companion Miguel live. The three men all lust after Faye, who enjoys being desired. The evening ends when Earle clubs the flirtatious Miguel on the head and Tod futilely chases after Faye in the woods, intending to rape her. Not long after this evening, Faye's father dies and Faye moves in with Homer as a "business" arrangement. Homer provides Faye's food and lodging and buys her elegant clothing so she can have a better chance at a movie career. Faye takes advantage of Homer's meekness and generosity, easily compelling him to allow Earle and Miguel to move into his garage.
Tod, newly uncomfortable with the violent lust that Faye's self-contained fantasy existence inspires in him, vows to avoid her. He puts away his sketches of her and concentrates on the other subjects he must draw for "The Burning of Los Angeles." Tod frequents Hollywood churches, each of which follow a different guide to salvation, but all of which contain the same type of fanatical, prophetic worshippers.
Homer and Faye seek Tod out after several weeks, convincing him to attend a cockfight Miguel and Earle are holding in Homer's garage. Tod brings along his screenwriter friend, Claude Estee. The dwarf bookie, Abe Kusich, also attends. After the violent cockfight, Claude, Abe, Earle, and Miguel sit in Homer's living room, drinking and lusting after Faye, who is barely dressed in unbuttoned silk pajamas. Tod and Homer remain removed from the party. Homer tries to talk to Tod about his feelings for Faye, but Tod no longer has patience to listen to admirers of Faye pine away, and becomes annoyed with Homer's slow explanations and clumsy attempts at friendship. The evening ends in excessive sexual desire and violence, as Claude and Tod save Abe from nearly being killed in a fight with Earle and Miguel. In the early morning, Homer and Earle discover Miguel in bed with Faye, which leads Earle and Miguel to fight.
The next day, Tod finds Homer in a nearly catatonic state. Faye has moved out and Homer has decided to return to Iowa. Tod leaves Homer alone for a few hours and goes downtown, where he gets trapped up in a large crowd waiting outside Kahn's theater for several movie stars to arrive at a premiere. Tod sees Homer walking near the crowd, still unresponsive and now carrying two suitcases. Tod watches as Homer sits on a bench near the crowd and Adore, a boy who lives in Homer's neighborhood, torments Homer from behind a tree, finally throwing a rock that hits Homer in the face. Homer gets up and chases the boy, stomping on Adore's back after the boy trips and falls.
Tod tries to pull Homer off, but before he can succeed, the crowd has jumped on Homer. The crowd riots and Tod is caught in the violent, sexual frenzy. To escape the reality of the mob's violence, Tod immerses himself in thoughts of his painting, "The Burning of Los Angeles," and the riot he plans to depict in it. Tod can no longer see Homer. Tod is eventually rescued by a policeman and driven away from the mob. The final image of the novel shows Tod sitting in the car, unable to determine whether the siren sound he hears is coming from the police vehicle or from his own mouth. He laughs and screams along with the siren from his seat in the back of the car.