The 1944 film (starring Charles Boyer, Ingrid Bergman and Joseph Cotten) was a Hollywood remake of a 1940 British version that starred Anton Walbrook and Diana Wynyard. This in turn was based on a 1938 play by the British novelist and dramatist Patrick Hamilton, who also wrote Rope (filmed in 1948 by Alfred Hitchcock). Hamilton's play was entitled Gas Light; both films had the title as one word.
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