Role in the film
In the opening credits, Nick meets Elizabeth James on the QE2 in 1986, and they eventually fall in love and wed on board, getting their picture taken by a photographer on there.
Shortly afterwards on October 11, Elizabeth gives birth to twins Annie and Hallie, but for some reason, she and Nick divorce shortly afterwards and she gets custody of Annie and takes her to London while he does so of Hallie and takes her to Napa, California with both parents deciding to not tell them about each other. He raises her with the help of his housekeeper, Chessy, while Elizabeth raises Annie in London. In summer 1998 Nick sends Hallie to summer camp at Camp Walden where coincidentally, Elizabeth sends Annie there as well, where they decide to switch places.
Annie returns to Napa and meets Nick for the first time but he doesn't know this. He thinks she is Hallie, takes her home, and introduces her to his fiancee, Meredith Blake, a 26-year-old publicist from San Francisco who is only interested in his fortune. The next day he takes Annie horseback riding and is about to tell her that he asked Meredith to marry him but she rides back to the house. When he catches up with her he asks her what she thinks about making Meredith a part of the family to which she says she likes it because he is going to adopt Meredith and give her a big sister to which he corrects her by saying that he is going to marry Meredith to which Annie flips out and starts yelling in French to which he is surprised because he never knew that Hallie could do so and tries to calm her, but she runs out upset. Then Meredith shows up and Nick informs her that "Hallie" didn't take the news well at all to which Meredith responds that she needs "a girl to girl chat" about the matter. Once Nick is out of earshot, Meredith threatens Annie that she's gonna marry Nick in two weeks "whether you like it or not".
In order to bring Nick and Elizabeth back together, Annie, Hallie, Charles, Chessy, and Martin conspire to have them meet at a hotel in San Francisco by arranging for Nick to meet Meredith's parents and by not telling Elizabeth about Meredith. Nervous about meeting Nick, Elizabeth asks Martin to accompany her and Hallie. After a few comical mix-ups in the hotel, Nick and Elizabeth see each other, Nick finally learns about the switch, and Annie and Hallie host a candlelit dinner for them, served by Martin and Chessy, on a yacht decorated to recreate their first meeting. During it, Elizabeth mentions that Nick didn't follow her after she left him. They make plans for Annie and Hallie to spend holidays together, but decide against resuming their relationship.
Annie and Hallie dislike this idea, so they force Nick and Elizabeth to take them camping by refusing to reveal which twin is which. After Elizabeth persuades Nick, Annie, and Hallie to take Meredith instead of herself, Annie and Hallie play tricks on Meredith, who becomes enraged and insists that Nick choose between her and them. He chooses the latter, and Meredith furiously breaks off the engagement. Although he still grounds Annie and Elizabeth for the shenanigans, he remarks to Elizabeth, "I got to remember to thank them one day".
Nick shows Elizabeth his wine collection, which includes the brand they drank at their wedding. She is touched by this gesture at first, but has a change of heart and returns to London with Annie. However, when they get home, they find Hallie and Nick waiting for them, having flown there on the Concorde. Elizabeth is fearful of remarrying, but she yields to Nick's confidence, and Annie and Hallie look on happily as they embrace. The closing credits feature photos of Nick and Elizabeth's second wedding, also aboard the QE2, with Annie and Hallie as bridesmaids and Martin presenting Chessy with an engagement ring.
- Ironically, seven years after this film was released, Dennis Quaid starred in the 2005 remake of Yours, Mine & Ours, where he plays a widowed coast guard with eight kids, who marries a widowed handbag designer (Rene Russo) with ten. But this time, the kids’ goal in that film is the total opposite of Annie and Hallie's in The Parent Trap; they want their parents to split up.