Peggy Sue prepares to divorce her high school sweetheart, Charlie Bodell, and is reluctant to attend their twenty-fifth class reunion. However, she delights her girlhood companions by arriving at the ceremony dressed in a vintage prom dress and wearing an antique locket that contains baby pictures of her two grown children. Catching up with an old friend, Peggy Sue confides that Charlie’s infidelity was a result of their decision to marry young, and, in retrospect, she would have made different choices if she was able to go back in time. When Peggy Sue is voted “queen” of the reunion, she faints onstage and regains consciousness in the year 1960, at a Buchanan High School blood drive. There, Peggy Sue’s odd behavior is ignored by her friends, who believe the girl fainted from loss of blood. However, Peggy Sue knows she is trapped in a time warp, and is astonished to revisit her past. At home, Peggy Sue has new appreciation for her mother’s domestic servitude, and is eager to establish a closer relationship with her younger sister, but remains antagonistic toward her father. Stepping back into her role as Charlie’s girl friend, Peggy Sue surprises the boy by agreeing to date other people. However, Peggy Sue’s newfound independence prompts Charlie to experience jealousy for the first time, and he is unhappy when she becomes close friends with Richard Norvik, an awkward genius who is ridiculed by his fellow students. Unknown to Charlie, Peggy Sue believes Richard’s mastery of physics can help her return to 1985, and she convinces Richard that she has experienced time travel by explaining future technology. Sometime later, Peggy Sue reunites with Charlie for a party, where he sings a cappella with his band. Peggy Sue remembers Charlie’s musical talent, and is seduced by his vows of eternal love. When they kiss in his car, Peggy Sue forgets that Charlie is still a teenager, while she has emotionally matured into adulthood, and he balks at her sudden desire for sex. Charlie is frustrated and humiliated by his girl friend’s erratic behavior, and reminds Peggy Sue of her promise to keep her virginity until they marry. After Charlie rushes Peggy Sue home, she wanders to a nearby café and flirts with an alluring outcast named Michael Fitzsimmons. Realizing she has a chance to revise her life story, Peggy Sue joins the boy on a motorcycle ride to the forest, where they smoke marijuana, star gaze, and make love. The next day, Peggy Sue visits Charlie at his father’s appliance shop and explains they are no longer compatible, but Charlie charms her and she realizes he will not be easily dissuaded. Charlie later hears rumors about Peggy Sue’s date with Michael Fitzsimmons and sneaks into her bedroom late at night. Overcome with rage, Charlie grabs Peggy Sue’s pillow to suffocate her, but she awakens and they creep downstairs to the basement to discuss their future. As Peggy Sue argues their marriage is doomed, Charlie is baffled by her accusations of betrayal and promises he will never break his vows of fidelity. Charlie declares he will never become a lecherous salesman like his father, but Peggy Sue knows otherwise and rejects Charlie’s pleas for reconciliation. When Charlie leaves, Peggy Sue joins Michael Fitzsimmons at a rhythm and blues club and turns down his proposal for a polygamous marriage in Utah. Although Michael argues their night of lovemaking is evidence of an eternal bond, Peggy Sue encourages the young man to filter his passion into poetry and suggests he write a book about their evening under the stars. Just then, Peggy Sue is surprised to see Charlie singing with the house band to a crowd of cheering fans, but she is unaware that Charlie is auditioning for a famous music producer, and leaves the club with Michael. The next morning, Peggy Sue apologizes to Charlie and he confides that the music producer dashed his hopes of becoming a famous singer. Crestfallen, Charlie reconsiders his desire for celebrity, and decides true love is more rewarding than social adulation. Peggy Sue is heartened by Charlie’s transformation, but continues to keep her distance. Back at Buchanan High, Peggy Sue bids farewell to Richard Norvik, who does not wish her to leave and proposes marriage. Explaining her disinterest in homemaking, Peggy Sue announces that tomorrow is her eighteenth birthday, and she must get away from Charlie because she got pregnant that day in 1960. Peggy Sue retreats to her grandparents’ country farm and they believe her story about time travel. On the evening of Peggy Sue’s eighteenth birthday, her grandfather escorts her to his Masonic Lodge and the secret society performs a ritual to send her back to 1985. As the old men chant, thunder strikes outside, lights dim, and Peggy Sue disappears. The gentlemen are convinced their mystic powers have transported Peggy Sue to the future. However, Peggy Sue is outside in a rainstorm with Charlie, who secretly followed her to the country. Although Peggy Sue protests her abduction, Charlie carries her to a nearby greenhouse and announces his decision to give up his music career. Believing Peggy Sue rejected him in fear that he would be an unsuitable provider, Charlie promises to take over his father’s business and proposes marriage, but Peggy Sue does not want history to repeat itself. Although Charlie is confounded by Peggy Sue’s unwarranted accusations of infidelity, he begs forgiveness anyway and hands her a birthday present: a locket with baby pictures of himself and Peggy Sue inside. Remembering that she wore the same locket to her class reunion, Peggy Sue mistakes the infants for her two children and realizes that ending her relationship with Charlie will sacrifice the lives of their offspring. As Peggy Sue embraces Charlie to make love, she travels into the future and awakens in a hospital room, where adult Charlie serenades her with a hushed rendition of “Peggy Sue Got Married.” Hoping to restore their love, Charlie vows to regain Peggy Sue’s trust and shows her the gifts she received while unconscious, including a book by Michael Fitzsimmons dedicated: “To Peggy Sue and a starry night.” Peggy Sue realizes her journey changed the events of her past, and invites Charlie home for dinner with his family.