 This is an adaptation of a Friedrich Dürrenmatt (qv) novel that  was based on a story he wrote for the 1958 German movie  _Es geschah am hellichten Tag (1958)_ (qv) (which had a slightly  different, not as dark ending). In that movie the murderer was  played by Gert Fröbe (qv) who would six years later play Auric  Goldfinger in the James Bond movie _Goldfinger (1964)_ (qv).