Amen - to sum up what it's about I quote from wikipedia:

Kurt Gerstein (August 11, 1905 in Münster, Westfalia - July 25, 1945), was a member of the Institute for Hygiene of the Waffen-SS and witnessed mass murders in the concentration camps Belzec and Treblinka. He is said to have contacted a Swedish diplomat as well as members of the Catholic Church with contacts to Pope Pius XII in order to inform the international public about the holocaust. In 1945 he wrote the Gerstein Report about this. Afterward he committed suicide.

A semi-fictional movie about his emotional search of his Christian values and ultimate decision to betray the SS by attempting to expose the Holocaust by way of informing the Catholic Church, Amen, was released in 2002, starring Ulrich Tukur as Kurt Gerstein and directed by Costa-Gavras.

Great movie!

I am in blood
Stepp'd in so far, that, should I wade no more,
Returning were as tedious as go o'er.