Ewald Balser plays Professor Manz in the German language version, but Roger Livesey plays Professor Manz in the English language version.
Friedrich Dürrenmatt wrote the screenplay (together with Hans Jacoby and Ladislao Vajda) while at the same time developing the novel form of the story under the title "Das Versprechen" (The Pledge). He finished the novel after the film was completed and gave it a different, much darker ending.