My Name Is Julia Ross (1945)

Julia Ross secures employment, through a rather-noisy employment agency, with a wealthy widow, Mrs. Hughes, and goes to live at her house. Two days later, she awakens in a different house in different clothes and with a new identity. She is told she is the daughter-in-law of Mrs. Hughes and has suffered a nervous breakdown. She soon learns that the son of Mrs. Hughes, Ralph, has murdered his wife, disposed of her body and, with his mother's help, plans to pass Julia off as his wife. And then plans to eventually kill her and pass it off as a suicide.