 When Mara Cecova, the arrogant and ill-tempered star of an avant-garde production of Verdi's "Macbeth" at the Parma Opera House, is injured after getting hit by a car outside the theater during an argument with the director, Cecova's young understudy, Betty (Cristina Marsillach), is given the coveted role of Lady Macbeth.In spite of her initial sense of foreboding, Betty is an instant success with her performance.However, an anonymous figure finds his way into the opera house on the opening night, watching Betty's performance from an empty box.