The book and movie are based losely on a similar real case (Friedrich Engel), without spoiling too much for new viewers.
Epilogue: "Hundreds of thousands of civilians were indiscriminately murdered by the SS and the German army in the Second World War during 'retaliatory measures'. In 1968 the so-called 'Dreher Law' was passed by the German Bundestag. This law allowed countless war criminals to escape justice."
The novel, whose text the film is based on, is written by Ferdinand von Schirach, grandson of the Nazi war criminal Baldur von Schirach, chief of the Hitler Jugend.