Tertuliano Máximo Afonso is a lonely history teacher who watches a film on a colleague's recommendation and notices an actor who looks exactly like him. Unable to let it go, he sets out to discover who this double is. The search leads to meetings that unsettle both men and threaten their ordered lives. Part thriller, part philosophical comedy, the novel explores identity, uniqueness and the fear of being replaceable, told in Saramago's distinctive, flowing style.