A man is stabbed to death, and all the signs are that his lover Terry Collins (Olivia de Havilland, Gone with the Wind) is the culprit. But it's impossible for Lieutenant Stevenson (Thomas Mitchell, Stagecoach) to prove this, as Terry has an identical twin sister, Ruth, and there's no way of demonstrating which one has the cast-iron alibi. From this gimmicky premise, director Robert Siodmak (The Spiral Staircase, The Killers) and producer/screenwriter Nunnally Johnson (The Woman in the Window) fashion a fascinatingly complex psychological film noir, as a psychologist (Lew Ayres, All Quiet on the Western Front) with a specialist interest in twins is brought in to help solve the crime. Delving deep into the personae of each sister, he finds himself falling in love with Ruth, which simultaneously helps him garner a better understanding of the twins' relationship while also putting himself in considerable peril. With the aid of impressively seamless special effects devised by the legendary