Former classical cellist Keith Reynolds (Guy Pearce) works as a music teacher at a high school in upstate New York. His predictable life as a family man is offset by his occasional work as a backup cellist with a symphony orchestra in the city. Lately, Keith has been reminiscing about his carefree youth. As the fall semester approaches, Keith and his wife Megan (Amy Ryan), along with their high school senior daughter Lauren (Mackenzie Davis), decide to take in a foreign exchange student from England named Sophie (Felicity Jones). In contrast to Lauren's active and gregarious personality, Sophie is more subdued and introspective.
At first Sophie is reluctant to open up to the Reynolds family. One day, while attending Keith's introductory piano class, Sophie reveals her remarkable talent as a pianist. Shocked by her talent as a musician, Keith becomes attracted to the young woman—excited about sharing his passion for classical music with someone. His wife Megan has never shown any interest in his music, referring to Keith's work with the symphony orchestra as merely "a hobby". When she sees her husband's growing friendship and attraction to the young exchange student, Megan becomes increasingly annoyed with the arrangement.