Jazz pianist Sebastian "Seb" Wilder, stopped in traffic in Los Angeles, snaps at aspiring actress Mia Dolan in the heat of the moment. Mia's subsequent audition after a challenging day at work goes wrong when the casting director makes a call during an emotional sequence. She is taken that evening to a sumptuous party in the Hollywood Hills by her roommates, who assure her that someone in the audience might help launch her career. She walks home dejected after her car is towed.
While performing at a restaurant, Seb deviates from the owner's instructions to exclusively play traditional Christmas music by incorporating jazz improvisation. As she walks past, Mia hears him playing. She walks into the restaurant, moves, and sees Seb getting dismissed for being a disobedient employee. Mia tries to complement him as he walks off, but he ignores her. Months later, she encounters Seb at a party where he performs in a cover band of 1980s pop music. Despite their obvious chemistry, they regret spending a great night together as they walk to their cars after the show.
When Seb shows up at Mia's place of employment, she takes him on a tour of the Warner Bros. backlot, where she works as a barista, and discusses her love of acting. She also mentions that she hates jazz. Seb, who couldn’t take that, drives her to a jazz club. He talks to her about his love of jazz and his ambition to start his club. Mia accepts Seb's invitation to watch Rebel Without a Cause, forgetting about her date with Greg in the middle of it. On the morning of the next day, she goes to an audition and returns sad because it does not go well. In the evening, she leaves the date with her boyfriend because she is bored and meets Seb in the theatre as the movie starts. When the showing is cut short due to a projector fault, Seb and Mia spend the remainder of the evening together, including a passionate trip to the Griffith Observatory.
After further fruitless auditions, Mia resolves to develop a one-woman show with Seb's help. They move in together as he starts to perform frequently at a jazz venue. Keith, a previous bandmate of Seb's, extends an offer for him to join his brand-new jazz fusion group, which will provide him with a reliable source of income. The same night, Mia shows a logo she made for Seb’s jazz club. Seb is not ready to accept Keith’s offer until he overhears Mia's attempt to convince her mother that he is pursuing his career. Despite his disdain for the band's pop image, Seb reluctantly joins it. The band is popular, but Mia knows that Seb dislikes the sound the band plays.
They both get into a quarrel about this, and Mia leaves the house. Mia performs her one-woman performance in front of a small group of people. Seb fails to be there at the show. Mia hears strangers talking about roasted reviews of her show. Seb tries to console her, but she gets broken and leaves for her home.
After seeing Mia's performance, a well-known casting director calls Seb and invites her to audition for a future film. She reluctantly attends after persuading her to go while traveling to Boulder City. The audition task for Mia is to recount a story. In response, she sings of being inspired to pursue her dreams by her aunt, a former stage actress who died as a direct consequence of alcoholism. Seb encourages her to concentrate on acting because he believes her audition went well.
Furthermore, he makes sure she gives everything she has when she has the chance because it is her dream. When Mia inquires about him, he replies that he will carry out his plan. By staying here and getting his things going.
Five years later, Mia has become a well-known actress and is married to another man; they have a daughter together. One night, the couple stumbles upon a jazz bar; Mia recognizes the logo she had once designed for Seb; she learns that Seb has started his jazz club; when he sees Mia in the crowd, Seb starts to play their love theme on the piano; a dream sequence develops in which the two consider what might have flourished their relationship along with their careers. Everyone gave him applause as they enjoyed his music. Before she leaves, they make eye contact and smile at each other, referring to their love that has never changed.
