Ann Lord (VANESSA REDGRAVE) is a terminally ill woman near the end of her life. Cared for by the night nurse (EILEEN ATKINS), she goes in and out of making sense, talking about Harris being her first mistake, and that the two of them killed someone named Buddy. All of which comes as news to her adult daughters, Nina Mars (TONI COLLETTE) and Constance Haverford (NATASHA RICHARDSON).
While the latter has led a mostly happy life with a husband and kids, Nina has drifted from one job and boyfriend to the next, meaning she isn't sure she can commit to her latest beau, Luc (EBON MOSS-BACHRACH). Thus, and thinking that her mom is experiencing the same sort of regret about life choices just like her, Nina tries to figure out if the people her mom mentioned are real, and if they are, how and when they fit into her life.
Fifty years ago, Ann Grant (CLAIRE DANES) is a young woman arriving at the coastal New England home of her best friend, Lila Wittenborn (MAMIE GUMMER). The latter is about to get married, with Ann to serve as her bridesmaid. That's all while Lila's high society mother Mrs. Wittenborn (GLENN CLOSE), focuses on the seating assignments for the reception, and Lila's boozing playboy type brother Buddy (HUGH DANCY) thinks she's marrying the wrong man. That's because he, Lila and eventually Ann, are all smitten with Harris Arden (PATRICK WILSON), the son of the family's former housekeeper who's grown up into a dashing doctor.
As the family dynamics play out over the next few days leading up to the wedding, Ann finds herself worried about Buddy but drawn to Harris, events that lead to those memories on her death bed so many years later, wondering about the decisions she made so long ago.