Bette Davis plays twin sisters, one glamorous, the other homely, in this tale of deception, betrayal, and murder. What makes the story so fascinating is its delicious irony, as the homely sister, Edith, becomes ever more ensnared in her own tangled web.
The story is marred slightly by some obvious contrivances and plot holes. But it has lots of twists and turns. And Bette Davis, with her memorable voice, her gestures, and those Bette Davis eyes renders the Edith character engaging, as she realizes something important that she had not foreseen, and then makes an effort not to be found out. It's all about the internal tension of faking a false identity.
Much of the plot is consumed in detail, as we watch Edith squirm and fret when confronted with small tasks like switching clothes with a corpse, faking a signature, or determining the combination to a wall safe. These action details are somewhat tedious. But they give Davis lots of opportunity to act.
The film's B&W cinematography is fine. The split screen technology wherein both sisters appear together in the same scene is rather self-conscious, but was quite advanced for its time. Rear screen projection is another technique that is used, but seems primitive by today's technical standards. The film's lighting is quite good.
The film gets off to a really good start with a snazzy, and very Hitchcockian, title sequence accompanied by Andre Previn's excellent original score. The film's supporting cast includes Karl Malden, Estelle Winwood, and Jean Hagen. But, though they are all credible in their roles, this film belongs to Bette Davis. It's her show. And a viewer's response to the film will hinge largely on their impression of Bette Davis and her ability to play two roles. Personally, I think she did a splendid job.