Vanni, fifty years old, is an established writer. Linda, thirty years old, collaborates on his novels in the shadows. They rent a penthouse apartment in the centre of Rome. Certain of their love, they have chosen to live together rather than get married. Their best friends on the other hand, Costanza and Alfredo known as the Prof (a famous heart surgeon), are married, wealthy, and manage their marriage like a business. One night, the Prof and Costanza burst into Vanni and Linda’s house. Costanza has discovered that Alfredo has a lover. This is the start of a long list of recriminations that will last all night, and reveal unexpected resentment pent up in both couples. Which of the two will be left standing the next morning in that penthouse become a battlefield?