On the eve of her twenty-fourth birthday, Carla Ardengo longs to escape her dreary existence, to find a new life. Visiting the Ardengos this evening is Leo Merumeci. He is a frequent guest because he is the lover of Carla’s widowed mother, Mariagrazia, and the holder of the mortgage on the Ardengos’ fashionable villa. Leo has become tired of Mariagrazia, who has been his mistress for fifteen years; he propositions Carla, and she agrees to come to his apartment the next day.

Lisa, who had been Leo’s lover and fiancee before he met Mariagrazia, is also at the villa. Mariagrazia suspects that Lisa and Leo want to renew their affair and that Lisa has come to her house to arrange a rendezvous. The object of her quest, however, is not Leo but Michele, Mariagrazia’s son. Just as Carla consents to give herself to Leo, Michele agrees to see Lisa.

Leo’s attempted seduction suffers a setback at Carla’s birthday party the next day. To make her more pliable, he fills her glass again and again with champagne, so that by the end of the meal she is drunk. They go for a walk on the villa’s grounds, where they happen upon an old shed conveniently equipped with a bed. Just as Leo prepares to have sex with Carla, she becomes ill from the wine, and he must wait until night to consummate the affair.

Lisa’s hopes, too, are temporarily dashed. She has lured Michele to her apartment with the promise of interesting a rich relative in him and so securing a good position for the youth. When Michele arrives the next morning, no relative is waiting. Lisa goes into the hallway, pretending to call him, but Michele sees that she does not even pick up the phone, and he leaves.

When Michele returns later that day, he finds Leo alone with Lisa; again Michele leaves. By the time he makes his third visit, Lisa knows all about Leo’s relationship with Carla. Michele accuses Lisa of chasing after Leo, but she replies that Leo would not have her; he already has Michele’s sister.

Although Michele does not feel anger on learning about his sister’s affair, he senses that he should act. He buys a cheap pistol, goes to Leo’s apartment, and tries to kill him. Michele has forgotten to load the gun, so his attempted murder fails. Carla, who has been sleeping with Leo, emerges from the bedroom to learn the cause of the confusion. Michele seizes the opportunity to urge her to abandon Leo, arguing that the family can sell the villa and pay Leo what they owe him.

Leo knows that if the Ardengos put the villa on the market they will get far more than the eight hundred thousand lira that they owe him. He will thus lose the house, his new mistress, and perhaps his old mistress as well. Consequently, he offers to marry Carla, allow the Ardengos to continue to live in the villa, and find Michele a job. Michele still opposes the marriage, but Carla consents because, even though she does not love Leo, she is eager for the money, fine clothes, and parties that the marriage will bring her.

Following the confrontation at Leo’s apartment, the two Ardengo children return home. Carla and her mother prepare to attend a masked ball, a fitting emblem of the life of concealment that they lead. Michele and Lisa, meanwhile, plan yet another tryst, and he promises that this time he will not rebuff her advances.