In Paris, seventeen-year-old Cecile shares an empty, sybaritic life with her wealthy playboy father Raymond, whom she addresses by his Christian name. While Cecile joins Raymond and Denise, his latest mistress, at a nightclub, she muses to herself that she feels “surrounded by an invisible wall of memories” and longs for the happiness that she felt the previous summer on the Riviera: Cecile, Raymond and his fatuous young mistress Elsa are vacationing at a villa by the sea when Cecile spots a young man floundering in the water with his disabled sailboat. Cecile dives in to help him, after which he introduces himself as Philippe, a law student vacationing with his mother at a nearby villa. Soon after, Cecile’s idyllic summer is interrupted when a letter arrives from Anne, an old friend of her late mother, who has decided to accept Raymond’s invitation to spend the summer with them. Anne’s imminent arrival requires a shift in sleeping arrangements, and so Raymond moves into the beach house, forfeiting the villa’s three bedrooms to the women. When the earnest Anne arrives, she is disturbed by Cecile’s nonchalance over failing her school examinations and shocked by the presence of Elsa, who is not much older than Cecile. As the days progress, Raymond begins to pay more attention to Anne, arousing the jealousy of Elsa and Cecile, who at times relates to Raymond more like a lover than a father. While they are all attending a casino in town one night, Elsa meets Pablo, a former lover from South America. When Raymond and Anne disappear, Cecile goes to look for them and sees them talking in Raymond’s car. After passionately kissing Anne, Raymond drives off with her, declaring that “he wants her.” Cecile, angry that Raymond has now targeted the “unattainable” Anne as his quest, lies to Elsa that Raymond drove Anne home after she became ill. Sniffing that she “refuses to be treated like a wife,” Elsa leaves with Pablo. The next morning over breakfast at the villa, Anne tells Cecile that she and Raymond plan to be married, and Cecile feigns happiness for the couple while seething inside. Later, Anne, concerned about Cecile’s welfare, prevents her from making love to Philippe and then forbids Cecile to see him again. After Anne asserts that Cecile should study rather than squander her vacation on pleasurable pursuits, Cecile vows revenge. When Elsa stops by the villa to pick up her belongings, Cecile decides to use Raymond’s former mistress to forestall his marriage plans. Enlisting Elsa in her plot, Cecile instructs her to move in with Philippe’s mother, then arouse Raymond’s jealousy by pretending to fall in love with Philippe. Later, the prim Anne complains to Cecile that they must spend the evening with the Lombards, Raymond’s business partner and his wife, who Anne disdains as promiscuous drunks. While at the nightclub with the Lombards, Raymond sees Elsa dancing with Philippe and becomes jealous. When Cecile makes a critical comment about Anne, Raymond observes that she sounds more like Anne’s mother-in-law than her prospective step-daughter. The next day, an excited Elsa informs Cecile that Raymond called to apologize and has asked to meet her the following afternoon. After lunch the following day, Raymond lies to Anne that he is joining the Lombards aboard their yacht, then sneaks out to meet Elsa. After Raymond leaves, Cecile secretly follows Anne as she takes a walk in the woods and spots Raymond making love to Elsa. Anne recoils in horror when she overhears Raymond confide to Elsa that he only promised to marry Anne so that she would have sex with him. Running back to the house, the sobbing Anne jumps into her car and drives off, ignoring Cecile’s pleas to stay. Soon after, word comes that Anne’s car has been found at the bottom of the sea. Her thoughts now returning to the present, Cecile realizes that Anne allowed them to believe that her death was an accident rather than a suicidal reaction to her betrayal. She has not spoken to Philippe since that summer, and Elsa is now living with Pablo in South America. Cecile and Raymond have an unspoken agreement never to mention the previous summer, and she cannot free herself of being imprisoned by a wall of memories. As she is removing her makeup, a defeated Raymond comes into her room and talks about going somewhere different, maybe Italy. Thinking of how futile their life is, her eyes well up with tears.