Once (Felix and Zelda Series)

Felix lives in a convent orphanage in Poland. He is convinced his parents are still alive and that they will one day come back to get him. When Nazi soldiers come to the orphanage Felix decides to escape and make his way home. The journey to find his parents is a long and difficult one, as Poland is occupied by the Nazis and a dangerous place for a Jewish boy. Felix manages to live and look after himself and another orphan, Zelda, with the help of a kind dentist, Barney, who is hiding and looking after a number of Jewish children. When the Nazis discover them, Barney makes the ultimate sacrifice for the children - electing to go with them on the train to the death camps, rather than taking the option of freedom offered by a Nazi soldier, one of his grateful patients.