Daryn is convinced that his sole goal in life is to get into Harvard, a dream his father, Xavier, relentlessly pushes him toward. One night, he meets Isabelle while trying to sneak into a rapper's concert and is instantly drawn to her. He courts and eventually falls in love with her, but when he confesses his love, she reveals that she has cancer and doesn’t have much time left.
Daryn crafts a plan to live a life in a year, and Isabelle recognizes his potential as a rapper and helps him to make his first demo CD. When they go to meet his parents, Xavier, disliking Isabelle, uses the moment to fire questions at her. He concludes that it is his responsibility to protect his son from distractions, such as girls; especially those like Isabelle. Feeling offended and rejected, Isabelle and her drag queen, parental figure Phil leave, and Daryn is left alone and depressed.
A few days later, Daryn is shortlisted at Harvard and attends his interview with Xavier. When asked what skills and abilities he has, he loses himself to memories of Isabelle. To his father's disappointment, he ends up saying exactly what Isabelle had made him realize—that all his accomplishments are in the grand scheme of a life he is living only for his father, and excuses himself. Later at home, Daryn quarrels with Xavier and is almost punched by him but his mother, Catherine, intervenes and stops the fight. Daryn goes to Isabelle and apologizes, deciding to abandon his family and leave town with Isabelle.
Isabelle and Daryn spend days together, and one day Daryn tries to surprise her by driving her to her mother Amanda's house. He convinces Isabelle to talk with her, but when she does, Amanda recognizes her but tells her to leave. Feeling rejected, Isabelle asks Daryn to drive away. While driving, an upset Isabelle starts yelling and shouting at Daryn, distracting him so he crashes into a bush near the beach. When Isabelle gets out, she becomes unconscious. Daryn calls for help, and manages to get Isabelle to the hospital.
A few days after Isabelle is discharged, Amanda comes to visit to apologize and explains to Isabelle why she left. Isabelle thanks Daryn for the opportunity to say goodbye to her mother. Catherine discovers that Daryn is back in town and decides to see him. Isabelle suggests that Daryn take a break from taking care of her just for the day, as Catherine is around. Daryn uses the opportunity to record his second song. When Daryn gets back, he finds Catherine panicking and Isabelle on the floor, unconscious and bleeding through her mouth. They get her to the hospital and discover that Isabelle's cancer has spread and her organs are shutting down. The nurse concludes by saying that Isabelle has only a few weeks left.
Soon after, they marry and consummate their love; Isabelle passes away a short time later. Daryn reconciles with Xavier and moves to New York City to pursue a career in music after graduating, but not before Isabelle posthumously leaves him one more surprise.
