Breakfast of Champions tells the story of the events that lead up to the meeting of Kilgore Trout and Dwayne Hoover, the meeting itself, and the immediate aftermath. Trout is a struggling science fiction writer who, after their fateful meeting, becomes successful and wins a Nobel Prize; Hoover is a wealthy businessman who is going insane, sent over the brink by his encounter with Trout.
Trout, who believes himself to be completely unknown as a writer, answers an invitation to appear at the Midland City arts festival. First he goes to New York City, where he is abducted and beaten up by a group of anonymous, faceless characters who through the media gain the moniker "The Pluto Gang". Trout hitches a ride first with a truck driver, with whom he discusses everything from politics to sex to the destruction of the planet. Then he hops a ride with the only clearly happy character in the book, the driver of a Ford Galaxie who works for himself as a traveling salesman.
Hoover gradually becomes insane as the book progresses. He terrifies his employee at the Pontiac dealership, Harry LeSabre, by criticizing his clothes. LeSabre is afraid Hoover has discovered that he is a closeted transvestite. A recent prison parolee named Wayne Hoobler attempts to find work with Hoover, but is rebuffed. With nowhere else to go, Hoobler hangs around the car lot. Hoover then gets into a fight with his mistress and secretary, Francine Pefko, because he accuses her of asking him to buy her a Kentucky Fried Chicken franchise.
Trout and Hoover meet in the cocktail lounge of the new Holiday Inn, where Hoover's gay estranged son, Bunny, plays the piano. When the bartender turns on the black lights and Trout's white shirt glows brilliantly, Hoover is entranced by it. He accosts Trout and speed-reads his novel, Now It Can Be Told. The premise of the novel is that there is only one creature with free will in the universe (the reader of the novel) and everyone else is a robot. Hoover interprets its message as addressed to him from the Creator of the Universe and goes on a violent rampage, injuring many people around in the belief they are unfeeling robots, including Bunny, Pefko, and Trout. Hoover is eventually institutionalized and winds up a homeless derelict.
In the epilogue, Trout is released from the hospital after Hoover partly bit off his finger in the rampage, and is wandering back to the arts festival, which unbeknownst to him has been canceled. The narrator, who has become an interactive character in the universe of his own creation, watches Trout and then chases him down. He proves that he is the Creator of the Universe by sending Trout all around the world, through time and back. Then he returns to his own universe, presumably, through the "void", while Trout yells after him, "Make me young!"
