Mavis Gary, portrayed by Charlize Theron, is a 37-year-old ghostwriter grappling with divorce and alcoholism. As she races against the clock to finish the final installment of her fading young adult novel series, she receives an email containing a photo of her high school boyfriend Buddy Slade's newborn daughter. This prompts her to believe that she and Buddy, played by Patrick Wilson, are destined to be together again. Resolute, Mavis departs from Minneapolis to her hometown of Mercury, Minnesota, under the guise of handling a real estate transaction.
On her journey, she indulges in nostalgia, listening to "The Concept" by Teenage Fanclub—an old favorite given to her by Buddy years ago. Upon her arrival, she plans a nostalgic reunion at a local sports bar. Meanwhile, Mavis visits Woody's, where she unexpectedly reconnects with an old acquaintance, Matt Freehauf, played by Patton Oswalt. Matt, who endured a traumatic experience that left him wheelchair-bound, cautions Mavis against her impulsive intentions of sabotaging Buddy's marriage. However, she chooses to dismiss his advice.
The next day, when Mavis meets Buddy at the sports bar, they encounter Matt again. Buddy extends an invitation to a gig featuring his wife Beth’s "mom rock band." As Mavis spends more time with Matt—who expertly brews bourbon in his sister Sandra's home—her infatuation blinds her even more. Mavis attends the concert, only to find herself the target of the other mothers' bitterness; they remember her as the "psychotic prom queen bitch." The lead singer, dedicating a song called "The Concept" to Buddy, exacerbates Mavis's feelings of inadequacy.
After a night of drinking, Mavis drives a tipsy Buddy home, where a shared kiss is abruptly interrupted by the babysitter. The following day, she faces her parents and receives an invitation to the baby naming ceremony for Buddy’s daughter. Despite drinking with Matt later that day, Mavis feels increasingly rejected and lonely. At the ceremony, she confesses her love to Buddy, but he turns her down, following which a chaotic incident leads her to reveal a long-buried pain—a miscarriage she endured years earlier after revealing her pregnancy to Buddy.
Buddy, busy setting up a drum set for Beth, overhears Mavis's outburst, discovering the emotional turmoil she has kept hidden. Feeling humiliated, Mavis departs the party and seeks solace with Matt, culminating in an emotional moment of intimacy. The next morning, as Matt sleeps, Mavis shares an insightful conversation with Sandra, who still idolizes her. Though Sandra wishes to join her in Minneapolis, Mavis opts to continue on her own, resolved to make a change.
While dining en route, Mavis finds her stride, penning the final chapter of her book, showcasing a protagonist who triumphs by leaving behind a troubled past and embracing hope for the future. However, as she reflects in the parking lot on her remaining car's damage—a remnant of her reckless behavior—the journey toward self-discovery truly begins.
