The story begins with Eloise "Ellie" Turner (Thomasin McKenzie) gracefully dancing in her room. A passionate aspiring fashion designer, she resides with her grandmother, affectionately known as Gran Peggy (Rita Tushingham). Despite her ambitions, Ellie lives with the shadow of grief from her mother’s untimely death (Aimee Cassettari), who occasionally materializes in her mirror reflections. When Peggy presents Ellie with a letter announcing her acceptance into a prestigious fashion school in London, Ellie is overjoyed, even as Peggy cautions her about the dangers lurking in the city.
Eager for her new adventure, Ellie embarks on a train journey to London and is taken to her new room by the taxi driver (Colin Mace), whose unsettling remarks leave her feeling uneasy. Choosing to dodge his gaze, she steps off at a nearby shop and eventually arrives at her room, where she meets her roommate, Jocasta (Synnove Karlsen). As they go out together, Ellie learns about her mother’s struggles with mental health leading to her tragic end. In the ladies' room, she overhears Jocasta making disparaging remarks about her, prompting Ellie to leave the pub. On her way back, she encounters a mysterious older man, a Silver-Haired Gentleman (Terence Stamp), who watches her with a smirk.
That night, while trying to sleep, Ellie is disturbed by Jocasta bringing a man back to their shared space. She steps outside to find a party in full swing, where her only ally is a kind classmate named John (Michael Ajao). Late the next morning, Ellie rushes to her first class just in time for attendance. Seeking solace and a fresh start, she relocates to a boarding house run by the enigmatic Ms. Collins (Diana Rigg), who lays down strict rules and lends Ellie the bedroom upstairs.
All at once, Ellie finds herself transported back to the vibrant and tumultuous 1960s. She enters the splendid Café de Paris, marveling at her own reflection as a young woman named Sandie (Anya Taylor-Joy). Intrigued, she observes Sandie's dreams of stardom and the unwanted advances of a rough patron. When Jack (Matt Smith) intervenes, only to charm Sandie, Ellie feels a strange connection to them both, leading to a series of surreal encounters across time. After witnessing Sandie's career aspirations, Ellie finds inspiration to create a stunning dress design mirroring Sandie's style.
As Ellie continues to navigate this spiral of the past and present, her excitement soon turns to dread. She uncovers darker truths about Sandie and Jack's relationship, revealing that the music industry is not as glittering as it seems when Sandie becomes entangled in a web of exploitation and abuse. Caught in her own battles with this haunting tale, Ellie grapples with her nightmares, the burden of her family’s history, and the ghosts of abused women from the past.
Despite her attempts at a semblance of normalcy, the shadows of the past loom large, and her psyche begins to unravel, culminating in terrifying hallucinations and violent confrontations. Desperate to understand the fate of Sandie, Ellie is propelled further into her traumatic history, where she discovers a sinister connection between Ms. Collins and Sandie that shatters her perception of time and identity.
In a dramatic climax, Ellie faces an unexpected betrayal as Ms. Collins reveals her true identity and the horrifying legacy of her life as Sandie. As flames engulf the house, Ellie is forced to confront the darkness of both their lives. In an act of selflessness, Ellie fights to save herself and John from the inferno, while Ms. Collins chooses to meet her demise on her own terms.
Months later, with the ghosts of her past finally laid to rest, Ellie triumphantly showcases her designs in a fashion show, surrounded by support from Gran Peggy and John. As she basks in her success, she is briefly reunited with visions of her mother's smile and the fading reflection of Sandie, acknowledging the scars of the past while embracing a hopeful future.
