[1] The film is a retelling of the 1886 novella Strange Case of Dr Jekyll and Mr Hyde by Robert Louis Stevenson set in 1950s France.

Jean-Louis Barrault plays Dr. Cordelier/Opale, the substitute for Dr. Jekyll/Hyde character; the film is also known for its visual style that is far above the normal television programs of the 1950s.

[2] In Paris, the lawyer Joly is given the will of his friend and client Cordelier, a well-known psychiatrist, who leaves everything to a patient called Opale.

The climax comes after a smart party at Cordelier's capacious house, when he is heard howling with pain in his laboratory.

Guilt over his sexual exploitation of female staff and patients led him, by long research into mind-altering drugs, to create a separate persona through which he could enact his hidden desires without taking responsibility.