Having moved from Arizona, Stargirl and her mother Ana arrive in Los Angeles to start a new life. Ana has gotten a job as a costume designer for a feature film, but the director is notoriously difficult to work with. While strumming in her room, Stargirl meets Evan, who lives in her new apartment building. He and his brother Terrell are making a sizzle reel for a potential film and would like her to write the music and possibly act in the film. While Stargirl has never acted before, she is convinced by the brothers and visits Terrell's workplace, a bar called Forte. Stargirl recognizes one of the regular visitors, known to the brothers as "Table Six", as Roxanne Martel, a one-hit wonder who left the music scene to become a producer; she is the actual owner of Forte.

Ana's busy work schedule leaves Stargirl to her own devices. She buys a pair of headphones for her grumpy neighbor, Mr. Mitchell, who begins to open up and reveals that he was once a film producer. Stargirl also meets with Roxanne to ask if she may use her song "Miracle Mile" for the sizzle reel, but Roxanne refuses, giving the impression that she is anti-social and bitter. Stargirl and Evan decide to write their own song, "Figure It Out", and Roxanne reveals that she denied them the use of her song to encourage them to create their own. She allows them to use a professional studio to record. Stargirl and Evan begin a romance.

Stargirl, Evan and Terrell finish the sizzle reel and send it out. As they wait for a response, Stargirl relates her past to Evan. Terrell eventually learns that an executive named Priya Collins has picked up the sizzle reel. She offers them a budget of one million dollars; enough to shoot their film. At home, Ana tells Stargirl that her film's production has shut down due to the director's behavior and that she has accepted a job in Berkeley. Stargirl is angry, as she is growing to love life in Los Angeles and realizes that Ana's issues stem from her fear of settling down. Mr. Mitchell advises her that one should learn from their mistakes and tells her that he was inspired by hearing her conversation with Terrell.