What is the theme in Into That Darkness: An Examination of Conscience by Gitta Sereny?

Good & evil and the human conscience are the main themes. Gitta Sereny reports that she wanted to be able to see what happened to Franz Stangl, how it was that he transformed into the man put on trial and held directly responsible for hundreds of thousands of deaths during his tours of duty at death camps during World War 2. In order to figure out what happened, she conducts numerous interviews.