The nephew of a Republican exiled during the Spanish Civil War is pushed to discover the fate of his uncle by a forgotten letter. Meanwhile, a researcher tries to discover what happened to another deportee after reading the novel "El impostor" by Javier Cercas. When the two coincide, they discover that the lives of their two ancestors are intertwined and end up unearthing the story of František Suchý and his son, who risked their lives and defied the Nazi regime from the Prague crematorium to save the ashes of more than 2,000 victims.
