Robert Rinder helps the second and third generations of three families affected by the Holocaust to retrace their relatives’ footsteps and discover the full truth about what happened to them. Robert also explores further his own family’s Holocaust stories. In the first episode, Robert meets Bernie Graham, who remembers that, when he was a child, his grandfather pointed to his missing eye and said 'Nazis', but Bernie doesn’t know what happened to him. Bernie has heard that his grandmother was sent to Auschwitz but survived until after the liberation. Bernie travels for the first time in his life to Germany, where his family were living before the Second World War. There he discovers the horrific story behind his grandfather’s injuries, and that his grandmother was forced to pay for her own transportation to Sobibor, an extermination camp in Poland, where she was murdered. Sisters Natalie and Louisa Clein know that their Dutch Jewish grandparents survived, but they have also been told that their grandmother’s sister Els died in the war. The sisters know nothing else about their great aunt’s fate. Natalie and Louisa travel to the Netherlands, where they find out about their grandmother’s incredible work in the Dutch resistance and how her sister Els was a famous dancer before the war. The trail takes them to a former Nazi transit camp, Westerbork, where Els was held, possibly for refusing the identifying star the Nazis decreed all Jewish people should wear. At Westerbork they discover the cruel twist of fate that thwarted Els’s chances of survival and led to her being murdered in Sobibor. For both sisters, their pain is mixed with pride at Els's extraordinary talent and character. Robert also embarks on his own journey of discovery. He visits the town his family came from in Lithuania and also travels to the Treblinka death camp, where he knows that his Polish grandfather’s parents and siblings died.

Robert Rinder continues his journey, meeting Noemie Lopian, whose French mother was arrested as a child by the Nazis. Noemie wants to follow in her mother’s footsteps to understand what happened and how her mother survived. In an extraordinary scene she meets the grandson of the man who hid her mother and her mother’s siblings in a chicken shed in his garden during round-ups of Jews in the town of Saint-Junien. Noemie also learns of the incredible sacrifice and courage of a young female French Resistance fighter who saved her mother’s life. Having discovered the fate of his grandparents in episode one, Bernie Graham is desperate to know what happened to his uncle Bernhard, after whom he is named, and who he believes committed suicide in Dachau concentration camp. To unravel what happened to his uncle, Bernie travels to Dachau, where he finds out that his uncle fell ill and died after a horrendous journey there. Despite the dark truths that Bernie uncovers, he hopes that we can learn from these terrible events. Robert’s mother's family were also impacted by the Holocaust, and he knows that his Polish grandfather’s parents and siblings died in Treblinka death camp in Nazi-occupied Poland. Robert travels with his mother to Treblinka to discover how her grandparents, aunts, uncle, great-aunts and great-uncle were murdered. They meet the last survivor of Treblinka, 92-year-old Leon Rytz, who tells his harrowing story. The three of them say Kaddish together, the Jewish prayer of remembrance for those who have died.