What happens when Tertuliano M-ximo Afonso, a professor of history, discovers at thirty-eight that there is a man living in the same city who is identical to him, but not related by blood at all. How do we know who we are? What do we mean by identity? What defines us as individual, unique people? Could we ever come to terms with the existence of another person with our voice, our features, our everything, down to the smallest distinguishing mark? Could we change places with our double without those closest to us noticing? Jos- Saramago's new novel can be read as an existential thriller, but it is above all a work of literature that immerses us in the essential questions of life.