Matt King (George Clooney
) is a Honolulu-based lawyer and the sole trustee of a family trust that controls 25,000 acres of pristine land on the island of Kaua'i. The trust will expire in seven years because of the rule against perpetuities, so the King family has decided to sell the land to Kaua'i native Don Holitzer for development. Just before family members are ready to officially endorse the deal, which Matt favors, a boating accident near Waikiki renders Matt's wife, Elizabeth, comatose.
Matt and Elizabeth have two daughters, 10-year-old Scottie (Amara Miller
) and 17-year-old Alex (Shailene Woodley
). Matt is not very close to his daughters and refers to himself as the "back-up parent." With Elizabeth in a coma in Queen's Hospital, Matt is forced to confront Scottie's inappropriate and Alex's self-destructive behaviors.
Matt learns that Elizabeth will never awaken from her coma, which means that under the terms of her living will she must be disconnected shortly from life support. He tells Alex, but not Scottie, that Elizabeth will not recover and must be allowed to die. Alex tells her father that Elizabeth was having an affair at the time of the accident. Matt confronts two family friends, Kai and Mark, and learns that Elizabeth's lover is Brian Speer (Matthew Lillard), a realtor who stands to benefit from the Kings' land deal.
Matt decides to tell Brian that Elizabeth will soon be dead to give him a chance to visit her while she's still alive. After telling the family of Elizabeth's terminal prognosis, Matt, along with the girls and Alex's slacker friend Sid (Nick Krause
), travels to Kaua'i to find Brian.
Matt goes jogging on the beach and passes a man that he recognizes from the real estate signs as Brian. He trails him and sees him enter a cottage, owned by Matt's cousin, Hugh (Beau Bridges).
Matt goes to the Speers' cottage and introduces himself as Elizabeth's husband. He tells Brian that he is there to let him know that Elizabeth will die in a few days and he wants to give Brian a chance to say goodbye. Brian says that while Elizabeth loved him, the affair was only a fling for him, and he loves his wife and family. He tells Matt he is sorry for the pain he caused.
Matt meets with his many cousins to vote on the fate of the family's 25,000 acres. The majority vote for Don Holitzer, but Matt has second thoughts and decides to keep the land and find a different solution. Shocked, Hugh tells Matt that he and the other cousins may take legal action, but Matt is undeterred.
At Queen's Hospital, Elizabeth is taken off life support. Her father visits and tells Matt he should have been a more generous and loving husband to Elizabeth, whom he describes as a good and faithful wife. Matt agrees with him, choosing to not disclose the details of Elizabeth's affair to her father. Later, Julie Speer (Judy Greer) arrives, telling Matt she is now aware of the tryst between Elizabeth and her husband. Julie forgives Elizabeth, even though she wants to hate her for destroying her family. Alex and Scottie say their final goodbyes, then leave Matt alone with Elizabeth. Finally coming to terms with his wife's betrayal, Matt tenderly kisses her and tells her goodbye. Later, Matt, Alex, and Scottie scatter Elizabeth's ashes in the ocean off Waikiki. The film closes with the three curled up on the living room couch, wearing Elizabeth's hospital blanket, eating ice cream, and watching March of the Penguins.