At the peak of the Great Depression, the Federal Theatre Project (FTP), steered by Hallie Flanagan, aims to deliver affordable theatre to millions throughout America. However, the FTP, along with other initiatives under the Works Progress Administration, grapples with mounting anti-communist scrutiny and intensified pressure from the newly formed House Committee on Un-American Activities.
In the heart of New York City, playwright Marc Blitzstein wrestles with creative block on his latest musical, The Cradle Will Rock. One day, during a public demonstration, he is visited by two imaginary entities symbolizing his deceased wife and the renowned German playwright Bertolt Brecht. They inspire him to inject the play with contemporary relevance rather than present it as an abstract notion. Motivated by their encouragement, he successfully completes the musical, which Flanagan greenlights as an FTP production, enlisting director Orson Welles and producer John Houseman for the project.
Amidst these developments, anti-communist FTP official Hazel Huffman organizes a gathering for fellow WPA employees sharing her views. At this meeting, Tommy Crickshaw, a ventriloquist involved with FTP's vaudeville initiative who feels dissatisfaction over his assignment with the talentless duo Sid and Larry, finds himself drawn to Hazel. While rehearsing the disturbing testimony she plans to present to HUAC, they grow closer; however, Hazel ultimately rebuffs Tommy's romantic advances. Experiencing a wave of despondency, Tommy oversleeps and discovers Sid and Larry taking center stage with his act. Following Hazel's eventual summons to testify before HUAC, her colleagues alienate her.
Simultaneously, Margherita Sarfatti, a delegate of Benito Mussolini's regime, visits New York to solicit backing from American industrialists for the war effort. She maintains connections with prominent figures such as William Randolph Hearst, Nelson Rockefeller, and steel tycoon Gray Mathers. Their pro-fascist inclinations create friction with his wife, Constance, who is an avid supporter of the arts and a friend to Houseman. Sarfatti facilitates the introduction between Rockefeller and Diego Rivera, who is commissioned to create a mural in the Rockefeller Center lobby. Tensions arise when Rivera's artwork, rife with communist symbolism including the portrayal of Vladimir Lenin, clashes with both Rockefeller and Sarfatti.
In the aftermath of Hazel's HUAC testimony, the WPA's future hangs in the balance as they face potential budget cuts. Although Flanagan makes a passionate case in front of HUAC defending the FTP, drastic measures follow: production funding is slashed, leading to widespread layoffs and an order to halt all ongoing projects, including The Cradle Will Rock. Now jobless, Tommy takes to the stage to perform a comedic routine, portraying his ventriloquist dummy as a Communist before walking off, leaving the dummy behind.
The production's opening night is thwarted due to FTP budget reductions, as the actors' guild refuses to allow a performance absent federal endorsement. Convicted not to succumb to defeat, Welles and Houseman, with the spirited support of Constance, orchestrate an impromptu performance in an abandoned theatre, featuring Blitzstein as both cast and orchestra. Male lead Aldo Silvano, struggling to provide for his family after distancing himself from his affluent parents due to their fascist views, reluctantly aligns with the union's decision to avert job loss. Meanwhile, female lead Olive Stanton must navigate a critical decision between the show and her established partnership with successful costar John Adair.
As Blitzstein launches into the inaugural song, the audience witnesses the other actors, including Aldo and a now-homeless Olive, spring to life and perform the entire play without ever stepping on stage. With the production drawing to a close, a jubilant celebration erupts among cast and audience alike. In parallel, workers dismantle Rivera's mural; Tommy shares a poignant embrace with a tearful Hazel in his dressing room; and a collective of former FTP artists conduct a mock funeral for Crickshaw's dummy, aptly renamed Federal Theatre Project. This procession culminates in present-day Times Square, decorated with billboards for Broadway productions.
