Lee (Casey Affleck) is a decadent and depressed repairman. After learning the news of the death of her brother Joey (Kyle Chandler), Lee returns to his hometown, Manchester by the sea, to deal with Joey's affairs. According to Joy's will, Lee will become the guardian of Joy's son Patrick (Lucas Hedges). Lee plans to bring Patrick back to Boston, but obviously Patrick is unwilling to leave his hometown and friends, but Lee is unwilling to stay in this sad place for long. It turned out that Manchester buried a desperate memory of Lee, whose mistake killed his two daughters in flames and his wife Randy (Michelle Williams) left him. Back in his hometown, Li once again met Randy, who had remarried and was about to become a mother. At the same time, Patrick's long-missing mother Alice (Gretchen Mol) also contacted Patrick, hoping that he could become a member of her new family.