Secret Beyond the Door

Secret Beyond the Door is a 1948 psychological thriller and modern updating of the Bluebeard fairytale, directed by Fritz Lang, produced by Langs Diana Productions, and released by Universal Pictures. The film starred Joan Bennett and was produced by her husband Walter Wanger. The blackandwhite film noir drama is about a woman who suspects her new husband, an architect, plans to kill her.

It turns out he was married before, his wife died suspiciously and they have a son. He also has a fiercely loyal secretary, Miss Robey, whose face is disfigured.Mark appears to be somewhat delusional and could be intending to murder Celia inside a room he keeps locked. The disturbed Miss Robey ends up setting fire to the house, whereupon Mark redeems himself in Celias eyes by saving her life. ........

Source: Wikipedia