England, on Christmas Eve 1991, the British royal family is gearing up to celebrate the holiday season at the Queen's Sandringham estate nestled in the picturesque countryside of Norfolk. Among the royal attendees is Diana Spencer, the Princess of Wales, portrayed by Kristen Stewart. Her marriage to Prince Charles, played by Jack Farthing, has significantly deteriorated due to his ongoing affair with Camilla Parker Bowles. As the extensive staff at Sandringham, under the skilled guidance of Timothy Spall as Major Alistair Gregory, prepare for the royal family's arrival, Diana takes to the Norfolk countryside in her convertible sports car, grappling with the impending pressure and turmoil that approaches.
On the brink of a mental collapse, Diana delays her arrival at Sandringham, crossing paths with Royal Head Chef Darren McGrady, portrayed by Sean Harris. During their encounter, she reflects on the long-abandoned estate of Park House, once her cherished childhood home. As her nostalgic feelings rise, she dashes towards a scarecrow, a wistful symbol of her past, unearthing an old jacket that once belonged to her father, John Spencer, the 8th Earl Spencer.
Upon reaching Sandringham, she is warmly welcomed by her sons, William and Harry, but she struggles to connect with the rest of the royal family, who largely overlook her presence. Her closest confidante at the estate is Sally Hawkins, who plays the pivotal role of Maggie, the Royal Dresser. Maggie continually encourages Diana to stand up against the royal family's expectations and navigate her royal duties. During her stay, Diana stumbles upon a book about Anne Boleyn in her bedroom, which sparks a series of haunting dreams featuring Boleyn, including a vivid hallucination of her at a Christmas dinner. In this vision, Diana imagines herself destroying a pearl necklace gifted by Charles and consuming the pearls in her soup, revealing her desire for freedom from her own royal constraints.
On Christmas Day, while attending the service at St. Mary Magdalene Church, Diana spots Camilla among the attendees, provoking a frantic media frenzy as journalists capture her every move. Afterward, she has a tense discussion with Charles about their sons' involvement in a pheasant shoot the following day, only to find him dismissive of her concerns and advising her to maintain a clear distinction between her private and public personas. In a private moment of deception, Charles orchestrates to send Maggie away to London while spreading unfounded rumors that she is the one responsible for placing the Boleyn book in Diana’s room and questioning her mental state. However, McGrady clarifies to Diana that Maggie had nothing to do with it.
Struggling with her own reality, Major Gregory attempts to compel Diana to adapt to royal norms, stating that the duty of British soldiers is to protect the Crown’s interests—interests that encompass her own. Diana, unwavering, counters his suggestion by declaring that she never requested anyone to sacrifice their life for her benefit. In a moment of despair, she imagines self-harm with wire-cutters gifted from McGrady, ultimately avoiding the formal Christmas dinner and instead escaping to her childhood home with the cutters in hand. Overwhelmed by nostalgic memories, she dances through the halls of her former abode, recalling her joyful childhood. Contemplating a drastic measure, she is briefly halted by the apparition of Boleyn, leading her to instead shred her pearl necklace in a moment of defiance.
On Boxing Day, Diana wakes to discover that Maggie has returned from London, and together they visit a nearby beach where Diana shares her struggles regarding her mental health and her marriage. In a heartfelt conversation, Maggie confesses her love for Diana, a sentiment that Diana kindly rebuffs. After parting ways, Diana confronts the reality of the pheasant shoot and boldly steps in front of the hunters to announce her intention to take William and Harry back to London, a proposition that Charles begrudgingly approves. As they embark on their journey, Diana engages in a lighthearted moment with her children, singing along to "All I Need Is a Miracle" by Mike & the Mechanics as they pass the scarecrow once more, now humorously adorned in one of Diana's outfits. They head to London, stopping for some Kentucky Fried Chicken, and enjoy their meal beside the River Thames. The film closes with Diana gazing across the river, filled with uncertainty about her future, yet liberated from the weight of royal expectations.
