A group of friends go on a boat trip to Lisca Bianca in the Aeolian Islands. Anna does not seem to be having fun like the others; she is touchy and prone to mood swings. When she mysteriously disappears, her architect partner Sandro and friend Claudia begin to look for her. Days go by; the pair become close and give in to the temptation of making love, both in their own way being unfaithful to Anna. They arrive in Taormina where their friends are gathered. Not having found Anna, it seems clear to Claudia that their relationship has become official. Instead, Sandro has a fling with someone else but Claudia seems ready to forgive him. At the time, the public was amazed by the fact that Anna's disappearance is neither explained or resolved. Filming took five months. The film took the Jury Prize at the Cannes Film Festival, Monica Vitti won a Golden Globe and a Silver Ribbon went to Fusco for the music. The film marked Antonioni's entry into the great book of the History of Film.