Highly intrigued by one of her teacher's lessons according to which you have to know how to lie, a young drama student, Sofia, decides to experiment with her talent in real life. But her lies ultimately uncover a bitter truth: her boyfriend and best mate are lovers. She therefore decides to tell the truth and nothing but the truth from then on. After a brief encounter with a fifty-year-old train ticket inspector, she stays faithful to her undertaking by proceeding to tell his wife what has happened. Tormented by guilt at what she has done, Sofia makes her way to Rome to participate in a casting, learning at the hands of an actress that acting is neither lying nor telling the truth, but simply creating an illusion, an illusion which somehow comes true when Sofia meets Gerard, the young French director with whom fate seems determined to unite her.