Grief-stricken over his partner Sydney's death, Gavin sets fire to every reminder in the couple's home before fleeing Los Angeles for New Jersey. There he hopes to find peace with the family of an old friend. Joan, the family's ten-year-old daughter, was born Highly Superior Autobiographical Memory, or HSAM: the rare ability to recall every day of her life in cinematic detail. She knew Sydney, and her uncanny mind contains startlingly vivid memories of him. In return for sharing her memories of Sydney, Gavin will help her win a songwriting contest she's convinced will make her unforgettable. But Joan's details about Sydney's final months force Gavin to question not only the purity of his past with Sydney but the course of his own immediate future.