On the eve of a world renowned string quartet’s 25th anniversary season, their beloved cellist, Peter Mitchell (Christopher Walken), is diagnosed with the early symptoms of Parkinson’s Disease. When Peter announces he wishes to make the upcoming season his last, his three colleagues find themselves at a crossroad. Competing egos and uncontrollable passions threaten to derail years of friendship and collaboration. Robert Gelbart (Philip Seymour Hoffman), the quartet’s second violinist, announces his desire to alternate chairs with first violinist Daniel Lerner (Mark Ivanir), after years of sacrifice and peacemaking for the benefit of the group. Robert’s wife, violist Juliette Gelbart (Catherine Keener) has a particularly difficult time grappling with the tragic diagnosis, as Peter has served not only as a colleague, but as a dear father figure since childhood.