Set against the backdrop of 1950s Hollywood, the story unfolds with Eddie Mannix (Josh Brolin), who starts his day by confessing his troubles at a local church. The priest, accustomed to Eddie's frequent confessions, listens as Eddie admits to hiding his smoking habit from his wife.
Eddie soon finds himself at a shoot for a young actress, Gloria DeLamour (Natasha Bassett), who's posing provocatively. After calling the police on the photographer, Eddie slaps Gloria twice to ensure her reputation remains intact and helps her assume a false identity for the press.
As a fixer for Capitol Pictures, Eddie’s role is vital in protecting the studio's stars from scandal. He reviews a rough cut of the upcoming historical epic, "Hail, Caesar!", featuring the popular actor Baird Whitlock (George Clooney) as the lead, Autolycus. To ensure that the portrayal of Jesus Christ is respectful across religions, Eddie seeks guidance from a diverse group of clergymen, which sparks an intriguing debate about the character of Jesus.
In addition to managing the epic film, Eddie is involved in the Broadway production of "Merrily We Dance." He introduces Hobie Doyle (Alden Ehrenreich), a rising Western star, who struggles to adapt to the demands of the theatrical director Laurence Laurentz (Ralph Fiennes). Despite Hobie's talent displayed in Western stunts, his heavy Southern accent proves problematic for the British-style dialogue Laurence demands. Hobie's repeated attempts to master the phrase "Would that it were so simple" lead only to frustration and hilarity.
During the filming of "Hail, Caesar!", an extra maliciously spikes a goblet meant for Baird. After downing the drink, Baird loses consciousness and is swiftly kidnapped. Eddie must now face the reality that DeeAnna Moran (Scarlett Johansson), a wholesome actress, is pregnant, complicating her public persona. Her dramatic reveal takes place during a mermaid scene, heightening the stakes for Eddie.
Once abducted, Baird discovers himself in a meeting with a group of disgruntled communist writers who aim to rally him to their cause. Meanwhile, Eddie receives a ransom demand of $100,000 from a mysterious group called “The Future.” While he deals with this crisis, he is pursued by journalist Thora Thacker (Tilda Swinton), who is probing into Baird’s past.
Eddie is also approached by Thora's sister, Thessaly, who wants inside information for her gossip column. Just as he begins to unravel the ransom situation, Hobie comes to his office, where Eddie reveals a suitcase filled with the ransom money. A visit to C.C. Calhoun (Frances McDormand), the editor of "Merrily We Dance," introduces another comical problem when her scarf gets caught in the film projector.
Eddie discovers that DeeAnna has an affair with a director who fathered her child. In a strategic move to protect her image, he decides to have her give the child up for adoption. They get Joe Silverman (Jonah Hill) involved as the adoptive father, further complicating matters.
Hobie experiences a glamorous evening at the premiere of his film "Lazy Ol' Moon," where the studio’s matchmaking efforts lead him to dine with actress Carlotta Valdez (Veronica Osorio). However, he soon realizes Burt, another actor, is involved in his own questionable business with the ransom money, leading to a chase.
In a twist, Hobie follows Burt and ultimately finds Baird, who has been urged to join the writers. Hobie, refusing to cooperate, takes Baird back just as the police move in on the writers’ hideout. When Baird tries to act disloyally against the studio, Eddie steps in to remind him of the importance of their reputations and the film's success.
As the narrative continues, Eddie faces a barrage of personal and professional dilemmas, including enticing gossip and competing interests. Eventually, he has a heartfelt reflection in confession, where the priest suggests that perhaps he isn’t so bad after all, encouraging Eddie to embrace his important role at Capitol Pictures and continue to take pride in his work.
With its unique blend of humor, drama, and Hollywood intrigue, the film captures the chaotic spirit of an era where reputation is everything, and the struggles behind the scenes are as compelling as those on-screen.
