Name That Trauma:: Lennart on a Late Ex-wife in a Laboratory Basement

I'm trying to remember a movie. Well, I probably have never known the title of the film due to the fact that I was very little (like 5-10 years old) when I saw it. I don't remember much of the film and the things I do remember are pretty much horror movie clichés, making it harder to figure it out, but I'll try to describe some of it as best I can remember. Here it goes:

Firstly, it was a semi-crappy B-movie. It could have been a ‘60s or ‘70s film as well as an ‘80s film. I remember it was a black and white flick but then again there was one scene (I'll explain later) where the police lights shined trough the window and that seemed to be in color, so let's say it was a color film. The plot was that a young(ish) woman was hired in a house to help out or maybe she got lost and asked for shelter there. In the house there lived an old man, a middle aged man (who started killing everybody or just held the woman captive) and there was at least one more character who was the man's brother/friend or neighbor.

One of the plot-twists was that the man kept his late wife in the basement. He might have had a laboratory-like basement and maybe he wanted to revive the dead wife somehow (maybe using the new female character for "parts"?) Then again I'm not sure about what the purpose of the basement was. All I remember is, that the dead wife was still wearing clothes (a white dress?) and the fact that the woman saw it, made the man angry and that meant that he could not let her out of the house to tell anyone about that.

As for the old man in the house, he was probably the man's father or maybe the owner of the house. He was very ill. He was on the bed, all the time and he could ring a bell (or push a button?) to down stairs to call for help. Maybe the woman was hired to be a nurse to the grandfather figure? At one point the old man asked to see a woman naked once before he passes away. I don't remember if the woman was forced to do so, or if she did it out of pity, but at one point she was mostly (maybe completely) naked, just standing there in front of him. There is a possibility that the nurse and the woman who was new to the house were two different people.

Later in the movie people started dying. Again, I don't know who the killer was or why he killed but it was probably the man. The old man was killed also, the call for help button was pushed and when the woman got up the stairs to see what's wrong, the old man was dead. At one point the woman tried to call for help with the phone, but somehow got in touch with the man's brother or neighbor who was also in on it, I guess. The woman saw the police lights through the window and thought that the help was on the way, only to find out that that was just the man's brother/friend with a pickup truck with the police-like lights on it. There was no escape. The brother/friend was in on the killing/harassing as well.

Sorry that was as much I could remember. This movie has haunted me almost my whole life and was the first movie that caused me nightmares and every now and again I remember some image of it. I am frustrated I can't remember the name of the film and rewatch it. I have read a bunch of plot summaries; none have been close to what I remember. Many of them are without spoilers so it makes things even more difficult.

If you can help me, I would be so very happy. It should not be a very rare movie since it was shown in my home land- Estonia in the (very) late ‘80s or early ‘90s.

PS. English is not my first language.

Thanks,

Lennart