During an unsuccessful attempt to compose a song in collaboration with a "very hip, very edgy" lyricist, Alex discovers that the woman who is temporarily watering his plants, Sophie Fisher, has a talent for writing lyrics. Alex, on a 48-hour deadline to write the song, asks her to help him, but she refuses multiple times, to the chagrin of her older sister Rhonda, who happens to be a huge fan of Alex. It's not until Alex composes a lovely song with some of Sophie's lyrics and plays it for her that she realizes they could do it. Over the next few days, they grow closer while writing the words and music together. Sophie reveals she had lost confidence in herself and abandoned writing after a disastrous romance with her English professor Sloan Cates.

Barely meeting the deadline Cora has set for the song's delivery, Alex and Sophie are thrilled when she accepts it; however, at a celebratory dinner with Alex's manager Chris and his wife, Sophie is mortified to encounter Sloan. She confronts him but finds herself tongue-tied in his presence, and Alex's own attempts to defend her result in a scuffle. Nursing their wounds back at Alex's apartment, Alex and Sophie fall into an unplanned romantic encounter.

When Cora invites Alex and Sophie to hear her interpretation of "A Way Back into Love," Sophie is horrified by her Indian-vibed, sexually confident interpretation of their earnest song. Alex rushes Sophie out of the room before she can say anything, and tells her he agrees it's awful but says they need to accept it as the cost of doing business. Later at Cora's party, despite Alex's best efforts to block her, Sophie finally tells Cora that she feels the new arrangement clashes with the insecurity expressed in the song's lyrics. Cora says she's still going to perform it her way, but expresses appreciation for Sophie's honesty. Sophie leaves Alex when she gets upset by his willingness to demean his talent and his claim that Sloan was right about her personality.

Sophie, intending to start a new life in Florida, reluctantly attends the opening of Cora's new tour at Madison Square Garden, at which Alex and Cora will debut "Way Back Into Love". Upon hearing that Alex is singing a new song "written by Alex Fletcher", Sophie, believing that Alex is stealing credit for her work; attempts to leave; but however, the song Alex sings is called "Don't Write Me Off", his plea for Sophie to give him another chance. A touched Sophie finds Alex backstage and he confesses to having successfully convinced Cora to drop the risqué version of "A Way Back into Love" in an attempt to win Sophie back. He and Cora perform the tune as he and Sophie intended it to be sung.

The end of the movie (an homage to VH1's Pop-Up Video) reveals that the song becomes a hit for Cora and Alex, the film version of Sloan's novel flops with critics and moviegoers (destroying his career), PoP! reunites for their induction into the Rock and Roll Hall of Fame, after which their lead singer Colin Thompson (who left the band with some of Alex's songs to start a solo career) winds up having his hip replaced after years of dancing, and Alex and Sophie go on to become successful partners, both in songwriting and romance, with five more new pop hits.