Harry Sanborn (Nicholson) is a New York music mogul with a libido much younger than his years. He has the world on a string -- and a string of beautiful young girlfriends to prove it.
During a romantic rendezvous with his newest girlfriend, Marin (Peet), at her mother's Hamptons beach house, Harry develops chest pains and eventually winds up being nursed by Marin's reluctant mother, Erica Barry (Keaton) -- a successful, divorced New York playwright.
In the process, Harry develops more heart pangs -- the romantic kind -- for Erica, a woman who is finally right for him in every way. However, some habits die hard, and when Harry hesitates to pursue Erica, his charming thirty-something doctor (Reeves) becomes smitten with her. Harry undergoes a true change of heart when he fights to win Erica back.