THE DARK MIRROR is a lesser-known entry into the canon of films noir that dominated Hollywood in the mid-Forties. Directed by Robert Siodmak (THE KILLERS), it is a psychological thriller focusing on the attempts of Lt. Stevenson (Thomas Mitchell) and psychiatrist Dr. Scott Elliott (Lew Ayres) to discover the killer of a well=established doctor. The only snag is that the chief suspects are a pair of identical twins, Ruth and Terry Collins, both played by Olivia de Havilland, who refuse to divulge any further information. Siodmak's narrative focuses in detail on the twins' psychology, by deliberately frustrating our desire to find out who is the 'good' and the 'bad' twin. The costume-designs apparently make this process of distinguishing quite straightforward - one wears white, the other black as the film unfolds - but the twins' responses to Elliott's psychological tests challenge our preconceptions. De Havilland has a rare chance to play the role of a 'bad' woman and grasps it with both hands; her Chicago accent is both harsh yet beguiling. It's clear that, as the 'bad' twin, she can seduce anyone she likes, even those men who proclaim their ability to see through any psychological games. Nunnally Johnson's script is taut and fast-moving (in the print I saw, the film lasts only eighty-one minutes), while Siodmak makes clever use of atmospheric lighting, especially shadows projected on the back will behind the twins, to suggest that they are somehow pursued by internal demons. THE DARK MIRROR might not be as celebrated as other films of similar genre, but it nonetheless captures some of the emotional uncertainties and moral that characterized the material of that period; its ending is particularly cleverly structured.