The Dark Mirror is a 1946 American psychological horror thriller film directed by Robert Siodmak starring Olivia de Havilland as twins and Lew Ayres as their psychiatrist.

It is revealed that Terry has an identical twin sister, Ruth, and the pair share a job and routinely switch places for their own benefit.

German-American filmmaker Siodmak’s The Dark Mirror is a melodrama representative of a Hollywood genre emerging in the 1940s concerning Abnormal psychology and its treatment through Psychoanalysis.

[5] The application of the techniques of German expressionism are evident through the use of chiaroscuro shadow, distortions in sound effects and dialogue and the use of mirrors to emphasize the psychotic descent of the characters, culminating in a “genuine tour de force.”[6] Siodmak directed a series of psychological dramas in subsequent years including Phantom Lady (1944), Christmas Holiday (1944), The Suspect (1945), The Strange Affair of Uncle Harry (1945) and The Killers (1946), the latter an adaption of Ernest Hemingway’s short story.

[7] When first released the staff at Variety magazine gave the film a mixed review, writing, "The Dark Mirror runs the full gamut of themes currently in vogue at the box office - from psychiatry to romance back again to the double identity gimmick and murder mystery.

But, despite the individually potent ingredients, somehow the composite doesn't quite come off...Lew Ayres is cast in his familiar role as a medico - a specialist on identical twins.

Copping thespic honors, despite a relatively light part, Thomas Mitchell plays the baffled dick with a wry wit and assured bearing that carries belief.

"[10] In a 9 February 1947 review in Australia's Daily Telegraph, Josephine O'Neill wrote: “This engrossing psychological drama frames a remarkable performance by Olivia de Havilland... so thoughtful and subtle that each girl becomes a clear-cut personality early in the film.

The quiet, distinguished production...obtains an extraordinary amount of suspense with the minimum of action... Robert Siodmak's clever, low-keyed direction is as unusual as his cast... (Lew) Ayres does a fine, sensitive, and charming job.

[14] The site quotes Richard Brody's positive review in the November 26, 2012, issue of The New Yorker: “ Its evocation of biological destiny wrenches the modernistic romance into tragedy.“ [14][12] The Dark Mirror was remade as a TV film in 1984 with Jane Seymour as the twins, Stephen Collins as the psychiatrist, and Vincent Gardenia as the detective.