Harry Sanborn is a wealthy New York music mogul who has had a 40-year habit of dating women under 30, including his latest conquest, Marin Klein. The two drive to her mother's Hamptons beach house expecting to be alone, but are surprised by Marin's mother, successful playwright Erica Barry, who is there with her sister Zoe.
After an awkward dinner, the night turns disastrous when — during foreplay with Marin — Harry has a heart attack and is rushed to a hospital. The doctor, Julian Mercer, tells Harry to stay nearby for a few days, so Harry ends up staying with Erica. Their personalities clash and make for awkward living arrangements—until they get to know each other. The fact that Harry is dating her daughter and that Julian has fallen for Erica leave the two struggling to deal with relationships.