Professor Nari, an eminent university lecturer, is slandered by a mysterious anonymous letter "accusing" him of making a banal error in an article on the subject of betrayal. Who could hate him so much as to slander him publicly? Suspicion turns into obsession and not even his relationship with the young Olivia can assuage his anxiety about the loyalty of the people who surround him. Even his wife Anna betrays him with a former student, while Professor Daverio, always the runner-up, and in love with Nari's wife for years, commits suicide; this seems to confirm the suspicion of his "guilt", until the true author of the attack is suddenly unveiled.