I saw this movie years ago and cannot remember the name, I remember there was a girl that lived with her rich aunt and I think the aunt was not real nice. I also remember there was this boy named Sam that she liked and her was considered a bad boy. I think the girls name was Margaret. What happened is the aunt ended up dying. I am not sure if the niece pushed her down the stairs, but I do remember that there was this nerdy boy who saw what happened. Sam ended up running and disappearing. Years later Margaret was living in the aunts house and married to the nerdy boy. I think he blackmailed her because he knew the truth behind her aunts death. Sam came back years late, but I can't seem to remember what else happened.

The Strange Love of Martha Ivers (1946) (http://www.imdb.com/title/tt0038988/)