old b&w about girl who witnesses murder of family as a child

I saw this movie as a kid; I think it was made in the ’50s. A young woman comes back to a house where she hid under the bed while an entire family was murdered. I think she is now engaged to the only remaining member of the family. She can’t remember exactly what she saw but every time she goes into the attic where she hid, she freaks out when she sees a white curtain blowing against an open window. I think in the end she remembers that the property caretaker was the one who committed the murders. I know it’s a long shot that someone else has seen this movie and remembers it, but endless Google/film site searches have turned up nothing.