One summery Saturday afternoon, a group of friends living in Rome departs on a yachting trip out to a local island. Two of the group, Anna (Lea Massari) and Sandro (Gabriele Ferzetti), young lovers considering marriage, have a dispute; that afternoon, Sandro announces that Anna is missing. A thorough search of the island is made on Anna's behalf, but she is never found, and Sandro, who remains relatively unconcerned, is never questioned. In fact, before the yachting group even returns to the mainland, Sandro tries to pick up Anna's best friend Claudia (Monica Vitti). Still, he is not even considered suspicious. Claudia and Sandro gallivant through the Italian countryside, supposedly investigating Claudia's disappearance, but their true motives are never clear, even in the last--entirely enigmatic--scene of the movie.—Mr Bongo