Just discovered this rarely shown gem from the past. It belongs to the period when psychology was at the forefront of detective murder stories, and it clearly owes a debt to Hitchcock's Psycho. The mother/son relationship is really rather chilling and very convincing. The detective parts of the story are straight from film noir - black and white, moody, much dashing about in cars, running up and down stairs in apartment blocks, the fetishism of semi-naked women in underwear and the mandatory stockings - so useful as a ploy to include scenes where women take them off and as murder weapons, and lastly but not least, the voyeurism of close-up strangulation. Not a perfect film by any means, but still a neglected classic.