Harry Sanborn (JACK NICHOLSON) is a wildly successful, 63-year-old record mogul who's never been married nor dates anyone over the age of thirty. His latest girlfriend is Marin (AMANDA PEET), a young auctioneer at Christies and the two have headed off for her mother's supposedly vacant weekend home for some frivolity.
To everyone's surprise, Marin's single, fifty-something mom, Erica Barry (DIANE KEATON), and Aunt Zoe (FRANCES McDORMAND) arrive on the scene. Everyone is fine with all four sharing the cabin, except for Erica, a successful playwright who doesn't approve of the May-December relationship, especially when she's all but given up on romance for herself.
Things take an unexpected turn when Harry has a sudden heart attack. The local doctor and big fan of Erica's work, Julian Mercer (KEANU REEVES), declares that Harry can't travel and thus must stay put until he improves. The only logical place for him to stay is Erica's place, another development she's not expecting, especially when everyone else returns to the city and then leaves them alone together.
Despite their differences, the two eventually start to become friendlier with one another, and with Harry and Marin mutually breaking up, romantic feelings begin to develop between them, much to their surprise. As longing turns into love, the two must figure out how to deal with their feelings and thoughts about what they should be doing in their lives, all while Erica must simultaneously deal with Julian falling for her.