The philandering writer Giovanni (Marcello Mastroianni) and his wife Lidia (Jeanne Moreau) visit the hospital bed of their old friend Tommaso, before making their way to a party. Over the course of the evening, the two wander and flirt, but not with each other. As Lidia considers the impending death of Tommaso, Giovanni gets closer to the beautiful Valentina (Monica Vitti), in this devastating portrait of love lost.