10 Rillinton Place (1971) Horror film
Middle-aged, married Christie lures unsuspecting young women into his home under the pretense of offering medical assistance, renders them unconscious with carbon monoxide gas, gets aroused by their limpid flesh, then strangles and buries them in his backyard. He takes a young, but desperately poor couple in as lodgers. The wife is pregnant, but he persuades the husband, John Hurt, into letting him perform an abortion on his wife and then attempts to pin the resultant homicide on him. John Hurt is fantastic as the illiterate boob of a hubby, Richard Attenborough is truly frightening as the unassuming killer and Fleischer manages to capture that stale, decrepit and palpable feeling of rot at the center of the story without ever going for obvious effects.
You can stream a fairly decent copy of it here, although I had a bit of trouble with it pausing here and there.
On Youtube there's also a documentary about the incident: here.