In Kenneth Lonergan's profoundly moving drama, Casey Affleck delivers a career-defining performance as Lee Chandler, a solitary and grief-stricken janitor in Boston who is forced to return to his hometown after his older brother Joe (played by Kyle Chandler) dies suddenly. Lee is shocked to discover that Joe has named him the legal guardian of his teenage nephew Patrick, played by Lucas Hedges, a sensitive and active high school student deeply rooted in his community. The arrangement forces Lee to confront the haunting memories and unspeakable tragedy that drove him away from Manchester-by-the-Sea years earlier, including his painful past with his ex-wife Randi, portrayed by Michelle Williams. As Lee struggles with his own crippling guilt and inability to move forward, he must navigate the practical challenges of caring for a teenager while being pulled back into a town filled with painful reminders. The film masterfully balances moments of devastating emotional weight with unexpected flashes of dark humor, creating an authentic and unflinching portrait of loss, responsibility, and the limits of forgiveness that resonates long after the credits roll.