In 1958, the questions and answers to be used for the latest broadcast of NBC's popular quiz show Twenty-One are transported from a secure bank vault to the studio. The evening's main attraction is Queens resident Herb Stempel, the reigning champion, who correctly answers every single question he is asked. Eventually, both the network and the program's corporate sponsor, the supplementary tonic Geritol, begin to fear that Stempel's approval ratings are beginning to level out, and decide that the show would benefit from new talent.
Producers Dan Enright and Albert Freedman are surprised when Columbia University instructor Charles Van Doren, son of a prominent literary family, visits their office to audition for a different, less difficult show by the same producers, Tic-Tac-Dough. Realizing that they have found an ideal challenger for Stempel, they offer to ask the same questions during the show which Van Doren correctly answered during his audition. He refuses, but when he nears a game-winning 21 points on the show, he is asked one of the questions from his audition. After a moment of moral indecision, he gives the correct answer. Stempel deliberately misses an easy question and loses, having been promised a future in television if he does so.
In the subsequent weeks, Van Doren's winning streak makes him a national celebrity, but he reluctantly buckles under the pressure and allows Enright and Freedman to start giving him the answers. Meanwhile, Stempel, having lost his prize money to an unscrupulous bookie, begins threatening legal action against NBC after weeks pass without his return to television. He visits New York County District Attorney Frank Hogan, who convenes a grand jury to look into his allegations.
Richard Goodwin, a young Congressional lawyer, learns that the grand jury findings have been sealed and travels to New York City to investigate rumors of rigged quiz shows. Visiting a number of contestants, including Stempel and Van Doren, he begins to suspect that Twenty-One is a fixed operation. Stempel's volatile personality damages his credibility, and nobody else seems willing to confirm that the show is fixed. Fearing Goodwin will give up the investigation, Stempel confesses that he was fed the correct answers during his run on the show, and insists that Van Doren must have been involved as well. Another former contestant gives Goodwin a set of answers that he mailed to himself two days before his quiz show appearance, which Goodwin takes to be corroborating evidence.
A guilt-ridden Van Doren deliberately loses, but NBC offers him a lucrative contract to appear as a special correspondent on the morning Today show. The House Committee for Legislative Oversight convenes a hearing, at which Goodwin presents his evidence of the quiz show's corruption. Stempel testifies at the hearing but fails to convince the committee, and both NBC network head Robert Kintner and Geritol executive Martin Rittenhome deny any knowledge of Twenty-One being rigged. Subpoenaed by Goodwin, Van Doren testifies before the committee and admits his role in the deception. After the hearing adjourns, he learns from reporters that he has been fired from Today and that Columbia's board of trustees will be asking for his resignation.
Goodwin believes that he is close to a victory against Geritol and NBC, but realizes that Enright and Freedman will not jeopardize their own futures in television by turning against their bosses. He silently watches the producers' testimony, vindicating the sponsors and the network from any wrongdoing, and taking full responsibility for rigging the show. Disgusted, he steps outside and sees Van Doren, who waves at him before boarding a taxi.
John Turturro as Herb Stempel
Rob Morrow as Richard N. Goodwin
Ralph Fiennes as Charles Van Doren
David Paymer as Dan Enright
Paul Scofield as Mark Van Doren
Hank Azaria as Albert Freedman
Christopher McDonald as Jack Barry
Johann Carlo as Toby Stempel
Elizabeth Wilson as Dorothy Van Doren
Allan Rich as Robert Kintner
Mira Sorvino as Sandra Goodwin
George Martin as Chairman Oren Harris
Paul Guilfoyle as Robert W. Lishman
Martin Scorsese as Martin Rittenhome
Griffin Dunne as Geritol Account Executive
Ben Shenkman as Childress
Timothy Busfield as Fred
Jack Gilpin as Jack
Bruce Altman as Gene
Joe Lisi as Reporter
Neil Ross as Twenty-One Announcer
Barry Levinson as Dave Garroway
Jeffrey Nordling as John Van Doren
Douglas McGrath as James Snodgrass
Stephen Pearlman as Judge Mitchell Schweitzer
William Fichtner as NBC Stage Manager
Illeana Douglas as Helena
Ethan Hawke & Calista Flockhart as Columbia Students