In 1946  the German emigre Robert Siodmak directed a trio of brooding hits that lifted his Hollywood pay grade from programmers to prestige pics, earning him a rare share of fame for a  director of the period. The creepy slasher The Spiral Staircase was a hit in February, his noir adaptation of Hemingway’s The Killers made headlines in August, and October brought the finely wrought psychological thriller The Dark Mirror. In ’47 he would receive a lengthy profile in LIFE magazine that makes proto-auteurist arguments while stating he was “just moving into the front rank of his profession.” The first two titles are ensconced as classics of their genres, and have long been available on home video, but  The Dark Mirror has been elusive until Olive Films released a a sharp looking Blu-Ray/DVD in September. Capitalizing on the spike in interest in clinical psychology following WWII, it winds together a traditional whodunit with a case study of a paranoiac, filmed with endless images of reflections and doublings by Siodmak.

LIFE reporter Donald Marshman attributes Siodmak’s sudden success to his ability to tap into “Hollywood’s profound postwar affection for morbid drama”. What Marshman calls “morbid drama” would later be termed film noir, but The Dark Mirror fits either term. In Nunnally Johnson’s screenplay of an Oscar nominated story by Vladimir Pozner, Olivia de Havilland stars in a dual role as Terry and Ruth Collins, identical twin sisters implicated in the murder of a prominent physician. While witnesses swear they spotted one of the sisters exiting the murdered doctor’s apartment building, it is impossible to determine which Collins girl they saw, and thus they are impossible to prosecute.  Lt. Stevenson (a brilliant Thomas Mitchell) refuses to bow to their apparent perfect crime, and asks psychologist and “twin expert” Scott Elliott (Lew Ayres) to study them for clues to their personalities. Elliott reluctantly agrees, and is soon falling in love with one, while suspecting the other might be a ravening lunatic.

Using effective optical printing work, de Havilland is able to play the two characters in the same frame without recourse to too many clunky back-of-head shots of body doubles. The gimmickry is mostly invisible, thanks to DP Milton Krasner and effects photographers J. Devereaux Jennings and Paul Lerpae. De Havilland’s subtle performances build on their efforts by instilling both sisters with shades of instability. Ruth is an innocent, both kind and weak, close to breaking down upon the first interrogation by Stevenson. Terry is forthright and aggressive, with an acerbic sense of humor. It is a matter of de Havilland softening or hardening her gaze, and this allows enough certainty for Siodmak to wring suspense out of Elliott’s psychiatric investigation. The two women circle each other in their spare apartment as mutual resentments build, Siodmak blocking the De Havillands like two demented tigers in a cage. Dr. Elliott does not engage them in a Freudian talking cure – no delving into the unconscious here – but a kind of investigative diagnosis, using Rorschach and polygraph tests until they reveal their true selves. Psychology is presented as simply another police tool, which the Lieutenant is eager to profit from, regardless of his potshots at Elliott’s taste in music and interior design.

Lew Ayres is interesting casting, because it was his first performance in four years, after he had declared himself a conscientious objector during WWII and was confined to an internment camp. He later relented, changing his status to “non-combatant” and serving in the Army Medical Corps. His career suffered due to this radically pacifist stance, working sporadically in features before a long career on TV. But as a man, and an image, of progressive principle, Ayres brings a sense of gravitas to this relentlessly logical character, a stereotypically tweedy intellectual, but with spine.

As impressive as the performances are in this film, and I haven’t had time to detail the blustery greatness of Thomas Mitchell, it is Siodmak’s direction that causes LIFE’s Marshman to swoon, and to even write an early version of the auteur theory, which Francois Truffaut at Cahiers du Cinema wouldn’t codify until his 1954 essay “A Certain Tendency in French Cinema”. Marshman writes in 1947:

Movie-making is a cooperative effort that can add up to nothing if one of the four principals [writers, actors, producers, directors] muffs his assignment. In a sense however, the director is the key man on the job, for his function is peculiar to the movies. The director personifies the only gadget which makes motion pictures a more glittering and fascinating and understandable form of entertainment and (sometimes) of art than any other. This is the camera, an instrument so fluid that it can believably transport an audience from a moldy temple at Angkor Wat to Grand Central Station in a single dissolve. …Movie directing is a specialized art, far removed even from something so closely related as directing a play.

This is a remarkable statement endorsing the director’s role as one exclusive to film, and is a more nuanced argument for the auteur theory (allowing that it is a collaborative art form) than the more polemical statement issued by Truffaut seven years later.

The Dark Mirror displays the “glittering and fascinating” possibilities of the art form through Siodmak and his production team’s ability to refresh a traditional whodunit with the language of postwar psychology, one in which the killer is revealed not through gunshots but by an inflection in De Havilland’s quavering voice.