After the death of his older brother Joe (Kyle Chandler), Lee Chandler (Casey Affleck) is shocked to learn that Joe has made him sole guardian of his nephew Patrick (Lucas Hedges). Taking leave of his job, Lee reluctantly returns to Manchester by the Sea to care for Patrick, a spirited 16-year-old. He is forced to deal with a past that separated him from his wife Randi (Michelle Williams) and the community where he was born and raised. Bonded by the man who held their family together, Lee and Patrick struggle to adjust to a world without him.