Twelve-year-old Rosie is a musical prodigy whose synesthesia allows her to see music in colors. Her mom has always pushed her to become a concert violinist, but this summer Rosie refuses to play, wanting a "normal" life. Forced to spend the summer with her grandparents, Rosie is excited to meet another girl her age hanging out on their property. The girl is familiar, and Rosie quickly pieces it together: somehow, this girl is her mother, when her mother was twelve. With help from this glitch in time―plus her grandparents, an improv group, and a new instrument―Rosie comes to understand her mother, herself, and her love of music in new ways.