As a young girl, Norma Jeane Mortenson (Ana de Armas) grows up under the care of her mentally unstable mother, Gladys (Julianne Nicholson). On her seventh birthday in 1933, she receives a framed photo of a man who her mother claims is her father. That very night, a fire erupts in the Hollywood Hills, prompting Gladys to take Norma Jeane there, insisting that her father resides nearby. However, their visit is cut short by police intervention, forcing them back home. In a fit of rage, Gladys nearly drowns Norma Jeane in the bathtub after she inquires about her father, but ultimately lets her go. Gladys chillingly states that her father abandoned them because he didn’t want Norma Jeane to be born.
Seeking refuge, Norma Jeane escapes to a neighbor’s house, where she finds solace. A few days pass before she is placed in a foster home while Gladys is committed to a mental institution, deemed unfit for parenting. Though she insists she is not an orphan, Norma Jeane is forced into the foster care system.
By the 1940s, she adopts the persona of "Marilyn Monroe," becoming a celebrated pin-up girl as her image graces magazine covers and calendars. However, her aspirations to break into acting come at a high cost; she is sexually assaulted by the president of a film studio, a man known as Mr. Z (David Warshofsky). This traumatic experience leaves her deeply scarred, leading her to cope by dissociating herself from the pain, allowing her character, Marilyn, to absorb the harsh realities of the industry.
In 1950, Norma Jeane auditions for a role in Don't Bother to Knock, but her performance crumbles as she breaks down in tears. Despite her emotional turmoil, the casting director recognizes her potential and grants her the role. A decade later, she visits her mother in the hospital, but Gladys fails to recognize her. Eager to uncover the truth about her past, Norma Jeane searches for any information regarding her father in studio records but finds nothing substantial.
As her career takes off, she develops intimate relationships with Charles "Cass" Chaplin Jr. (Xavier Samuel) and Edward G. "Eddy" Robinson Jr. (Evan Williams), with whom she engages in a polyamorous arrangement. Her breakout moment comes with the 1953 film Niagara. However, when spotted in public with Cass and Eddy, the studio head admonishes her to limit her public appearances with them, intensifying her internal struggle between the public persona of Marilyn and her true self.
Joyfully discovering she is pregnant, Norma Jeane grapples with the fear that her child could inherit her mother’s mental struggles and opts for an abortion. Yet, on the day of the procedure, she has a change of heart, but tragically, it is too late. While she becomes a household name, earning a fraction of what her male co-stars earn—$5,000 per film compared to their $100,000—her sense of worth diminishes.
Her path crosses with Joe DiMaggio (Patrick Brennan), a retired athlete who resonates with her desire to transcend Hollywood’s superficiality for more serious roles in New York City. While she films Gentlemen Prefer Blondes, she receives a letter from a man claiming to be her father, Tygh Runyan. Exuding intense disconnection during the film's premiere, she expresses that the portrayal is not truly her. Later, she encounters Joe again at her hotel, where he proposes, and she reluctantly accepts.
However, their marriage rapidly deteriorates after Joe’s anger erupts when he receives nude publicity photos of Norma Jeane from Cass and Eddy. Following a violent confrontation, she moves forward with filming her most iconic scene in The Seven Year Itch, yet domestic turmoil looms large. Soon after, she divorces Joe.
In 1955, she auditions for a Broadway play written by the illustrious Arthur Miller. While her performance captivates most, Arthur initially seems unimpressed. He gradually softens as she provides profound insights about the character Magda, who parallels her own troubled existence, reviving a spark within him. They marry and move to Maine, as Norma Jeane relishes the joys of domesticity and awaits a child. Unfortunately, she suffers a miscarriage, thrusting her back into the chaotic world of acting.
As the years wear on, particularly during the filming of Some Like It Hot, Norma Jeane spirals into uncontrollable breakdowns and feels increasingly isolated from Arthur. The relentless media scrutiny plagues her, triggering frequent outbursts, especially towards director Billy Wilder (Ravil Isyanov). To manage her escalating stress, she turns to substance abuse.
By 1962, the weight of fame takes a toll as she becomes mired in a dependency on drugs and alcohol. During a troubling encounter with President John F. Kennedy (Caspar Phillipson), she is manipulated into compromising situations, all while grappling with the reality of her existence as "Marilyn Monroe." Overwhelmed, she hallucinates, reliving moments of her past, including another abortion, before returning home to Los Angeles.
As she receives a call from Eddy informing her of Cass's death, she resists confronting the truth he left behind. Ultimately, she opens a package from him revealing a beloved childhood stuffed tiger and a heart-wrenching letter confessing that the letters she thought were from her father were actually sent by him.
Devastated by the unveiling of this secret, Norma Jeane tragically succumbs to an overdose of barbiturates. In her final moments, she envisions her father, who welcomes her to the afterlife, leaving behind the confounding legacy of Marilyn Monroe.
