The film is told from three perspectives: interviews with the show's three lead writers: Jess Oppenheimer (who was also the show runner) (Tony Hale), Madelyn Pugh (Alia Shawkat), and Bob Carroll Jr. (Jake Lacy); flashbacks; and preparations for a live filming in 1953. Today a show with 15 MM viewers is a mega hit. I Love Lucy had 60 MM viewers.In 1939, Lucille Ball (Nicole Kidman), 28, is an actress contracted to RKO Pictures. She gets small parts in big studio productions, but featured mainly in low budget films which gives her the moniker "Queen of the B-Movies." She is cast in the comedy Too Many Girls, a film Pugh describes as a bad stage play made into an even worse movie. She meets one of the film's casts, charismatic 22-year-old Cuban singer Desi Arnaz (Javier Bardem) and they fall in love instantly. Months after filming, they marry and buy a home in Hollywood. Arnaz has a successful stint fronting the Desi Arnaz Orchestra that tours around the country, while Ball continues her film career with little success. After Arnaz serves in World War II, he resumes his success with his orchestra, with Ball having to accompany him because of his infidelity.Ball finally gets a break when she is cast in 1942's The Big Street. The film is only a modest hit, but Ball's performance is praised. She meets with RKO President Charles Koerner (Brian Howe) confident she will get better scripts on par with established stars like Rita Hayworth and Judy Holliday. Instead, he terminates her contract as several actresses RKO loaned to other studios will be returning and there will be nothing for her (Plus she is 35 years old now). He suggests she use her voice for radio, and with no substantial film roles coming, she does. In 1948, she is cast in the radio show My Favorite Husband, which becomes a massive success.The show draws interest from CBS (Producers Howard Wenke (Clark Gregg) & Joe Strickland (Nelson Franklin)) and cigarette company Philip Morris (rep by Roger Otter (Jeff Holman)), who suggested to turn "My Favorite Husband" into a television show. Ball agrees but only if Arnaz plays her on-screen husband. The executives initially refuse because Arnaz is Cuban, but later concede after Ball refuses to give them the copyright of the show. She also hopes that working with Arnaz will decrease his infidelity and save their marriage.By 1953, the show is renamed I Love Lucy and becomes a smash hit with nearly 60 million viewers each week. A three-camera system, designed by Arnaz, allows viewers on the East Coast of United States to see the show live and without static (since the show is filmed on the West Coast). During production, Ball deals with several issues on the show; Vivian Vance (Nina Arianda) and William Frawley (J.K. Simmons), who play the Ricardos' married neighbors the Mertzes, do not get along, and Frawley is often drunk on the filming set. The crew goes about their normal production day. The dynamics are complex. Lucille is very particular that her character on the show should not come across as dumb or dimwitted.Ball also clashes with the directors (Donald Glass (Christopher Denham), to whom she declares that she has no confidence in his abilities to direct the show) and writers during table reads and scene blocking. Lucille has the ability to imagine the scenes as they are being narrated to her, and this gives her the ability to almost predict audience reactions to the jokes and sense check if certain situations and premises would make sense or not. Particularly troublesome is a scene where Arnaz comes home and covers Ball's eyes while she is setting the table, and she names several different men before he reveals it's him. The couple announce to CBS and Phillip Morris executives that Ball is pregnant. Jess is troubled as Desi wants the pregnancy to be shown on air, while Jess knows that CBS will never allow it. Jess and Desi clash over Lucille's rude attitude towards the other crew members of the show.The executives insist Ball hide the pregnancy behind large objects, but the couple refuses and proposes the pregnancy be shown (though they are never allowed to say the word "pregnant" on air). Lucille continues to undermine Donald's authority during the scene rehearsals. Lucille also comes down hard on Vivian for losing weight. She says that losing weight is not in line with Vivian's character of Ethel. She says that most women want to see themselves on the show, which is a fat, plump Ethel.Ball also deals with Arnaz staying out late, and a photo emerges in the tabloids of him with another woman. Desi tells Lucy that he plays cards on a boat with some other celebrities and sleeps there when he is too tired to come home, and that the picture was taken six months ago. She reluctantly believes him. Frawley has Ball understand that Arnaz's infidelity may stem from her making the business and creative decisions on the show which makes him feel emasculated, though she explains to everyone that he is the one who makes all the decisions. She asks Oppenheimer to give Arnaz a producer credit, hoping it will stop Arnaz's infidelity and save the marriage. Instead, Oppenheimer reminds Arnaz he has top billing, as he is the person saying "I" in I love Lucy, in attempt to placate him. Arnaz responds by sharply scolding Oppenheimer for trying to patronize him.The night of the live filming, a newspaper article deems Ball a Communist, though she was cleared during a HUAC hearing months ago. Ball admits she registered as a member of the Communist Party when she was young and influenced by a relative, but Arnaz insists she lie to the public and claim she accidentally marked the wrong box. Ball refuses to lie to the public, fearing she will be humiliated. Arnaz cancels his usual show warm up with the audience, and instead addresses the audience about the accusations (It's a big gamble, because if the gamble doesn't work, then the show is over then and there). He takes a live call with FBI Director J. Edgar Hoover, who assures all of the audience that Lucy has been cleared of all the charges.As the couple celebrates backstage, Ball shows Arnaz a handkerchief with lipstick on it. Arnaz says it's hers, but Ball shows him another handkerchief with her own lipstick on it, proving Arnaz's infidelity. When filming begins, Ball momentarily loses her concentration. They start over, with Ball being more focused. The film ends with a title card saying Ball filed for divorce after the taping of their last show in 1960.