http://www.imdb.com/title/tt0116643/
Harold Guppy moves into the Beasley household as a lodger. Before long Mrs. Beasley falls for him and eventually ends up in his bed. Her 13-year old daughter Joyce is aware of what is happening and threatens to tell Mr. Beasley unless she is also allowed share the bed with Harold and "Mum". "Mum" seems to think there is no harm in this, as long as Joyce doesn't take part in the physical activities. Harold gets caught up in a web of deceit and blackmail and each time he tries to break free of the grasp of "Mum" she threatens to tell the police that he has been abusing Joyce. The film continues much in this line, and it examines the effect of the relationship on both Harold and Joyce and how they are both driven to extreme action because of the influence of Mrs. Beasley.
AND...
Perverse, well-acted (Julie Walters cheery, mother-knows-best, psycho-bitch performance is not to be missed), and endlessly interesting little-seen English film tells the odd tale of how in the early 1950's one very ignorant young man unwittingly got himself involved with one very demented old gal and her equally disturbed teenage daughter soon after renting a room out of their home. Comparable to "The Young Poisoner's Handbook" in atmosphere, and in it's morbidly gleeful presentation of strange, little heard true-crime stories. "Intimate Relations" is an oddly enjoyable film if you allow yourself to be on the same twisted wave length as the flick. Eye-brow raising scenes galore fill this movie, I'll admit, and a good deal of creative liberties are taken with the true story on which this film is based. I still, regardless of all, highly recommend "Intimate Relations" if you can get your hands on it. Because, I am of the opinion (like previous reviewers have stated) that seeing a movie like this is almost healthy now and then in that it jars your senses and makes you grateful that your family isn't as messed up as the one witnessed in this movie!
I think this may just have crashed into my top ten required
