The film opens with a warm greeting from its director, Leos Carax, and the writers, Sparks, as they invite the audience on a journey through the vibrant streets of Los Angeles. The story centers around Henry McHenry, portrayed by Adam Driver, a stand-up comedian renowned for his outrageous and controversial style. In front of an enthusiastic crowd, Henry shares insights about his recent engagement to Ann Defrasnoux, played by Marion Cotillard, a celebrated opera singer. He reflects on the transformative effect she's had on him, though he's unsure of how.
When reporters swarm after a performance, Henry humorously dances to deflect the attention. As their love develops, both sing passionately about their swift romance, revealing they are now married and living in her secluded mansion in the woods. At the opera house, the Conductor, which is Simon Helberg, works as Ann's piano accompanist, expressing his aspirations to conduct orchestras while secretly harboring feelings for her. However, Ann, while deeply in love with Henry, confesses her fears of him, fueling tension in their relationship.
The couple soon welcomes their daughter, Annette, who is presented to the audience as a wooden marionette but adored by the characters as a typical baby girl. Amidst this, Henry's nerves about fatherhood gradually seep through. During a car ride, Ann dreams anxiously about six women making disturbing accusations against Henry and a harrowing motorcycle crash.
As the story unfolds, Henry embarks on a Las Vegas tour where he shocks his audience by announcing that he "killed" Ann, using dark humor about tickling. This unstable revelation leads to his abrupt fall from grace as his career begins to crumble while Ann's star continues to rise, despite her growing unease about their relationship.
In a desperate attempt to reconnect, the couple takes a fateful yacht trip that spirals out of control during a violent storm. Amidst the chaos, Henry's drunken behavior exacerbates their conflict, ultimately leading to Ann’s tragic demise as she is seemingly pushed overboard. Left alone with Annette, Henry rows to safety, only to be haunted by Ann’s ghost, who promises to forever linger through their daughter’s voice.
When law enforcement investigates Ann's disappearance, they conclude it was an unfortunate accident. Henry, still processing his loss, becomes enchanted by Annette's singing talent, which brings him unexpected solace. As Henry invites the Conductor to discuss exploiting Annette's gifts through a global tour, tensions rise when the Conductor reveals feelings for Ann and secrets about their past.
The world quickly becomes enthralled by Annette's extraordinary talent, while Henry indulges in newfound fame, leaving child-rearing largely to the Conductor. However, jealousy and anger consume Henry when he discovers the Conductor’s influence over Annette, culminating in a tragic confrontation where Henry drowns him, oblivious to Annette witnessing the horror.
Attempting to shield her from show business, Henry schedules one final performance at the Hyper Bowl Halftime Show. When Annette freezes on stage, she finally speaks the haunting line, "Daddy kills people." This revelation plunges Henry into a downward spiral, leading to his arrest for the connected murders that haunt him.
As he faces trial, Henry refuses to testify but grapples with visions of Ann, who sings alongside him about hypothetical changes to their past. Following his conviction, we see Henry each day, now alone, overshadowed by his crimes and the ghost of Ann who has remained relentlessly by his side.
In a poignant prison visit, Annette, now perceived as a real little girl by Henry, struggles to forgive him, making it clear he has lost everything he had once loved. As she is escorted away, Henry turns to the audience, pleading for them to abandon their gaze upon him. The lifeless marionette of Annette rests forgotten on the floor, symbolizing the tragic fallout of their destructive love.
