Sorry, but 'Sorry, Wrong Number' loses a lot in its transition to the screen. For one thing, there are too many flabby flashbacks--a form quite popular in the '40s but used extensively in this film, ad nauseum. All of the suspenseful action in the bedroom of the bedridden victim is held at bay while we watch another endless flashback attempting to show us how selfish and unworthy this woman is. If you heard the original radio drama with Agnes Moorehead giving a spine-chilling portrait of Leona, you'll see why the film becomes too diffuse in an attempt to give us "filler material". The fact that Lucille Fletcher adapted her own work for the screen would give the viewer hope that this is going to be just as good as the radio drama--but it's not. Barbara Stanwyck gives an excellent performance, bordering on hysteria toward the finale--but it's an actressy performance and not as controlled as some of her other film noir roles. Burt Lancaster has a colorless role and can't do much with it. Ann Richards is impressive as the woman who tries to warn Leona. By expanding the plot outside the bedroom, Fletcher created a confusing number of sub-plots that simply take away from the tension. Too much padding actually hurts the film. Anatole Litvak's direction is strong--but not strong enough to put the film on the same level with the classic radio drama. The plot is overcomplicated to the nth degree.
Trivia note: The only other film with such heavy use of flashbacks to tell a complicated story is THE LOCKET ('47), but it was done more efficiently than it is here.