Alex Fletcher (Hugh Grant) is a once-famous pop star from the British group 'PoP!' who has come to terms with his "has-been" status. He's busy entertaining nostalgic fans at various gatherings and looks forward to his participation in "Battle of the 80's Has-Beens," where forgotten stars face off in the boxing ring. However, a twist arises when his manager Chris Riley (Brad Garrett) informs him that Cora Corman (Haley Bennett), a young megastar, has expressed a desire for him to write a song for her. The title of the track is "A Way Back Into Love," which she wishes to perform with Alex at Madison Square Garden in just two weeks.
Cora admires Alex's music, as his songs helped her cope with her parents' divorce during her childhood. Nevertheless, pressure mounts when Ray (Matthew Morrison), Cora's manager, reveals that seven other retro artists are vying for the same song title, emphasizing the urgency for Alex to deliver by the end of the week. Despite his initial reluctance to compose again after two decades—since he always relied on his ex-partner Colin (Scott Porter) for lyrics—Alex's manager convinces him that a pivot in his career is necessary, as interest in his nostalgia concerts is dwindling.
In a serendipitous turn of events, Alex discovers that the woman watering his plants, Sophie Fisher (Drew Barrymore), has a knack for writing lyrics. Desperate to meet his deadline, he appeals to her for help. Initially resistant to the idea, Sophie eventually sees potential when Alex plays her a beautiful melody featuring her lyrics. Over the next few days, their professional partnership deepens into a personal connection as they collaborate on the song.
Sophie confesses that her confidence has been shattered following a chaotic breakup with her English professor, Sloan Cates (Campbell Scott). This toxic relationship left her feeling inadequate, especially after discovering that Sloan wrote a successful book based on her life—portraying her as a brilliant imitator with no unique voice. Meanwhile, Alex reveals his own struggles with Colin, as Colin's solo career took off after stealing their past songs, while Alex's solo efforts have languished.
As they race against time to finish the song, they celebrate their success when Cora accepts it. However, during a dinner with Alex's team, Sophie is horrified to face Sloan, prompting her to escape to the bathroom in distress. Alex supports her during this moment, offering to help her practice a speech to confront him. Their interaction spirals into unexpected romantic encounters, adding complexity to their blossoming relationship.
The two continue to navigate personal and professional challenges as Sophie accompanies Alex on various gigs, lifting his spirits during self-doubt. When Cora's rendition of "A Way Back into Love" deviates drastically from their original vision, Sophie speaks out against the reimagining, leading to tension. In a moment of frustration, Sophie asserts that she can't work without inspiration, prompting her to leave Alex.
However, the next day, Alex learns that Sophie has sent Cora new lyrics, spurring him to pursue her to the opening of Cora's tour at Madison Square Garden. Sophie mistakenly believes Alex is taking credit for her work, prompting her to leave when she hears him sing a new song titled "Don't Write Me Off," a heartfelt plea for her forgiveness. Touched and moved, she finds Alex backstage, where he reveals he convinced Cora to adopt the original version of their song, once again bringing them together.
The film concludes with an homage to VH1's Pop-Up Video, showcasing their success after the song becomes a hit for both Cora and Alex. Meanwhile, Sloan's film adaptation of his book flops, leading to his career's demise, and 'PoP!' reunites for their induction into the Rock and Roll Hall of Fame. In a final twist, Alex and Sophie thrive both creatively and romantically, composing five additional pop hits together, cementing their partnership in both life and music.
