In Milan, Lidia (Jeanne Moreau) suddenly storms out of a posh gathering held to honor her husband, Giovanni (Marcello Mastroianni), who has just written a new novel. Distressed at the news that her friend Tommaso (Bernhard Wicki) has a terminal illness, Lidia begins roaming the streets of the city, questioning her marriage to Giovanni. Meanwhile, Giovanni, seemingly oblivious to his crumbling relationship with Lidia, attempts to seduce beautiful ingénue Valentina (Monica Vitti).