Old Late 40's Early 50's Movie Title

[moviegeek54]

I saw this move as a child several times but can't remember title. Plot goes something like: Young woman (18 to early 20's) returns to house she lived in as a child until she suffered some sort of mental breakdown. After years of therapy in a clinic, she is much better but still suffers from recurring nightmares/visions of a room in a house, stairs, and most key here, some wallpaper print that continues to haunt her memory. My vague memory of the main point of this film is that she suffered the breakdown as a child after witnessing a murder (perhaps her mother?) and has blocked out the incident. I think the gardener or stable man or such killed her (not sure here). Anyway, the murderer watches her closely for any signs of her remembering what she witnessed. I think she finally finds the room and the wallpaper she keeps envisioning that was either painted over or covered with different paper. Any help here would be appreciated. Thank you.