Although director Robert Siodmak is most closely identified with noir classics such as The Killers, Crisscross, and The Phantom Lady, The Dark Mirror is a fine addition to his portfolio. Expanding on the scope of his creativity, Siodmak relies heavily on the performance that he draws from star actress Olivia De Havilland. The Dark Mirror is a psychological thriller about a murder committed by one of two twin sisters; Ruth and Terry Collins. Playing both sister roles, De Havilland's acting ability and developmental character depth is tested. De Havilland passes admirably. At first the twin sisters seem physically and emotionally similar. Subltle nuances differentiate their personalities and it is De Havilland's fine acting that peels away the layers of emotionalism that define each sister's character traits. De Havilland aided by keen camera work by Siodmak, keeps viewers on edge as she shifts roles within frames that are shared by both sisters. ( I still don't understand how Sidomak achieved this- especially the scenes when Terry is comforting a terrifed Ruth.) When Terry attempts to drive Ruth insane, thoughts of Gaslight come to mind, but De Havilland's dual performance creates even more interest. Dimitri Tomkin's musical score is also a plus as it serves to accentuate the emotions that heighten the film's climactic expressions shared by the twin sisters. The script by Nunnally Johnson, is sometimes mundane, and it seems that the film's eighty- five minute running time is consciously stretched. The film's ending is a surprise as Terry's wrath and frustration finally surface.