Don (Robert De Niro) and Ellie Griffin (Diane Keaton) are long-divorced, but when their adopted son's ultraconservative biological mother unexpectedly decides to fly in for the young man's nuptials, they are forced to play the happy couple to avoid an awkward situation. With their heartily amused friends and adult children looking on, Don and Ellie must confront their past, present and future -- and hopefully avoid killing each other in the process.