A look at a seemingly placid New England town that is actually wrought with illicit affairs, crime and tragedy, all told through the lens of Olive, whose wicked wit and harsh demeanor mask a warm but troubled heart and staunch moral center. The story spans 25 years and focuses on Olive's relationships with her husband, Henry, the good-hearted and kindly town pharmacist; their son, Christopher, who resents his mother's approach to parenting; and other members of their community.
Olive visits Christopher and his second wife in New York, but abruptly returns to Maine, where she gets some bad news about Henry, and ultimately befriends a lonely widower she meets while out for a walk.
Christopher suggests counseling to Olive after she and Henry have a scary episode following dinner with friends. Later, Christopher confronts his mother about how she treated him as a child.
Kevin returns to Maine and Olive is able to convince him to stay over and attend Christopher's wedding-rehearsal dinner. Olive clashes with the bride's mother and scares the flower girl at the ceremony.
Math teacher Olive Kitteridge attempts to help Kevin, a smart but timid student whose mother is suffering from depression. Her son Christopher isn't happy though. Henry goes on a hunting trip that concludes with a tragedy.