Based on the play The Deputy by Rolf Hochhuth, the film examines the political and diplomatic relationship between the Vatican and Nazi Germany during World War II.

During World War II, Kurt Gerstein, a Waffen-SS officer employed in the SS Hygiene Institute, designs programs for the purification of water and the destruction of vermin.

He is shocked to learn that the process he has developed to eradicate typhus, by using a hydrogen cyanide mixture called Zyklon B, is now being used for killing Jews and other "undesirables" in extermination camps.

They drive by German soldiers digging up and burning the bodies of previously murdered Jews in a mass grave near the camp, and the Doctor asks Gerstein if he knows any contacts to help get him out of Germany.

The film is based on a 1963 play by Rolf Hochhuth, The Deputy, a Christian Tragedy, which was widely attacked in Catholic and Jewish circles[citation needed] for its portrayal of Pope Pius XII.