In 1980, 19 year old Lady Diana Spencer attends a party thrown by Prince Charles at Buckingham Palace and meets Camilla Parker Bowles, Charles' mistress ("Underestimated"). Meanwhile, Queen Elizabeth II is looking for Charles to get married, and he brings up Diana as a possibility, although he has recently broken off a relationship with her older sister Sarah. The Queen encourages Charles to begin the courting process, as she believes Diana would be perfect for what the staff calls ("The Worst Job in England").
Charles sends Diana a necklace and invites her to a performance by cellist Mstislav Rostropovich. There, she meets Camilla again and starts to become a lot more suspicious of her and her relationship with Charles. While the performance is going on, she imagines a more punk-rock version of the concert, more in line with her interests ("This Is How Your People Dance"). After the performance, as Camilla watches Charles and Diana leave, Camilla ponders that Diana is the people's idea of a princess. ("That Is How Your People Danced")
The press takes note of Diana's growing relationship with Charles and starts hounding her ("Snap, Click"). Charles is still unsure about marrying Diana, but the Queen tells him that he can keep his close relationship with Camilla while marrying Diana. Charles proposes to her, but tells Camilla he will break it off if that's what she wants. Camilla tells Charles to go ahead with the wedding, and he assures her he will be there for her. A nervous Diana moves in to Buckingham Palace ("Whatever Love Means Anyway"). Soon after, despite some reservations from Diana, she and Charles get married ("I Will"). Camilla's husband Andrew, having affairs of his own, assures Camilla that they will make their own complicated marriage work ("I Will (Tag)").
Diana's first public appearance happens in Wales, and even though the townsfolk are skeptical at first, they, as well as the whole country, become enamored with Diana. Charles starts to become jealous of Diana's newfound fame ("The World Fell in Love"). Camilla tells Charles that Andrew has cut off all his other relations, hoping to reignite their own marriage, and Camilla breaks up the affair, saying she would be the most hated woman in England if she was found out. ("You Do Your Duty") Diana tells Charles that she is pregnant ("A Baby, Charles)" and soon after their son William is born. Diana walks in on Charles talking sweetly on the phone to Camilla, who he hasn't talked to in months. Camilla says that Andrew is being stationed more and more overseas. Diana is very hurt by Charles' lack of affection towards her and becomes depressed, even after having their second child, Harry. This culminates in her smashing a window with her hand ("Simply Breathe").
Sarah convinces Diana to fight back and do more with her power, so she decides to become more and more involved with charity, leading to even more popularity, especially after a surprise performance at the Royal Ballet Christmas Gala ("She Moves in the Most Modern Ways"). Charles is enraged at this and reminds Diana that her only achievement is marrying him ("The Rage"). Diana realises this might be the end of any hope of love in her marriage ("As I Love You"). Charles visits Camilla late at night and she says she still loves him and would like to continue their affair ("I Miss You Most on Sundays"). Diana decides to use the press and newfound popularity to get back at Charles and fight back against the norms of British society. Despite Charles' attempt to fight back, she succeeds and becomes more popular ("A Pretty, Pretty Girl").
Barbara Cartland, novelist and Diana's step-grandmother, introduces the audience to James Hewitt, a war hero who has recently come home. He and Diana begin their own affair ("Here Comes James Hewitt"). Barbara notes that the two affairs between Diana and James as well as Charles and Camilla are filled with more love and happiness than Charles and Diana's marriage ("Him and Her and Him and Her"). Diana tries to talk to Charles, but he wants to "(Just Dance)". Charles' valet Colin lets him know of Diana and James' relationship, but he decides to let it go as he is happy with Camilla.
Despite Charles’ worries, Diana goes to a clinic for AIDS patients and bonds with the men there ("Secrets and Lies"). Soon after, Diana learns from Sarah that Charles and Camilla go out almost every night with their friends, and Diana decides to crash a party for Camilla's sister. At the party, their friends, usually bored by Charles, are excited that they get to witness ("The Main Event") which leads to a confrontation between Diana, Camilla, and Charles. On the car ride home, Charles reveals he knows about Diana's relationship with James, which he says he doesn't care about and that the boys will be fine as long as they both love them ("Whatever Love Means Anyway (Reprise)"). Diana is excited to tell James, but he reveals that he has been stationed in Germany and will be there for two years. ("I Do My Duty") Diana, suspecting Charles, vows to get revenge ("Pretty, Pretty Girl (Reprise)"). The press increasingly hounds Charles about his failing marriage ("Snap, Click (Reprise)"). Diana contacts Andrew Morton, a writer who is writing a book on her, and agrees to give anonymous quotes to him, bashing Charles, Camilla, and the monarchy. The book is published and is the talk of the country ("The Words Came Pouring Out").
Charles tries to get the Queen to meet Camilla, but she refuses. Charles decides to go on TV, tell the truth about his affair, and try to win back some favour from the public ("I Miss You Most on Sundays (Reprise)"). Diana learns about the interview from Paul, her butler and friend, who comes up with the idea that she draw attention away from it by wearing a "F-You" Dress ("The Dress"). As the Palace Staff laments, ("Staff Quartet") The Queen agrees to a divorce between Diana and Charles. She laments that it didn't work out while reflecting on her own marriage ("An Officer's Wife"), and tells Diana "don't be foolish". Diana is excited to start a new life with her boys, but it is tragically cut short by a car accident. Charles and the company tell the audience that "the people who will change the world are not the ones you think will change the world." ("If (Light of the World)")
