Set in the 1830s, the narrative follows Rosina da Silva, portrayed by Minnie Driver, who is the elegant eldest daughter of an affluent Jewish family within a tight-knit community of Sephardic Jews in London. Following the shocking murder of her father, which leaves the family in dire financial straits, she firmly rejects an arranged marriage with an older man and resolves to support her family herself. Even if it means taking the stage like her esteemed aunt, known as Countess Koulinskyi, a famous singer.
Determined to reinvent herself, she adopts the name Mary Blackchurch—a Protestant of partial Italian descent—to hide her true heritage. Quickly, she secures a position as a governess for the Cavendish family, a Scottish landed gentry residing on the picturesque Isle of Skye in the Hebrides. Charles Cavendish, played by Tom Wilkinson, is a science enthusiast preoccupied with the challenge of retaining photographic images on paper. Meanwhile, his wife, portrayed by Harriet Walter, drowns in her own boredom.
Their young daughter, Clementina (Florence Hoath), is initially resistant to Mary’s authority, yet she eventually finds a close friend in her. Mary, possessing a remarkable education and a thirst for knowledge at a time when women's roles were largely domestic, astounds Charles with her insight and capability, leading her to become his invaluable assistant. Their bond deepens into an emotional and passionate connection.
On the eve of Passover, while in her room, Mary accidentally spills salt water on one of Charles’s prints, which leads her to discover a groundbreaking technique for image preservation. This revelation brings them together in more ways than one, culminating in an intimate moment that strengthens their relationship.
However, complications arise with the return of the Cavendish son, Henry (Jonathan Rhys Meyers), who returns home after a string of expulsion-worthy escapades at the University of Oxford. Obsessively fixated on Mary, he uncovers her concealed past. Although he vows to keep her secret, he ultimately confesses his feelings to Charles. The father harshly dismisses his son's affections, calling Mary "practically a demimondaine," which creates an emotional rift between them.
In a moment of vulnerability, Mary leaves behind a nude photograph of Charles, leading him to recoil from her. When a colleague visits, Charles unjustly takes full credit for the technique they developed together, leaving Mary feeling betrayed. Frustrated, she shifts her anger onto Henry before deciding it’s time to leave the island and return to London.
Reclaiming her heritage, she presents herself again as a Jew and confronts Mrs. Cavendish at the dinner table with the intimate portrait of her husband. Back in London, she fully embraces her identity, becoming a renowned portrait photographer celebrated for her unique depictions of Jewish life. As her sister announces her next scheduled sitting, she is unexpectedly met with Charles, and when asked if they have completed the session, she coolly responds, "quite done." Her reflective closing remark lingers: >"I hardly think of those days at all. No, I don't think of those days at all." However, the portrait of Charles remains a poignant reminder among her collection, revealing a deeper, unspoken connection in her heart.
