Every one knows Franco is off his rocker. But this film is from a period where it wasn't so abundantly clear from looking at the screen.
For those that think Franco is a hack film maker with all the sleazy zooms of his later films, see this and you'll discover that he does that because he likes it, not because he doesn't know how to do anything else.
This one is made very nicely. It's shot in black and white holds up very well today, comparing favourably with many other films from this era and genre. Plot wise it's a serial killer movie, but it has that real timeless feel and atmosphere that places it firmly in the horror category.
The understated performance from Franco regular Howard Vernon is outstanding, but all the cast are great. I'm not sure what the original language is, probably Spanish, I've seen it in English and French and although they're both acceptable, it's a shame not to hear the real actors voices (although Vernon probably dubbed himself).
It's also amazingly daring for 1962, in fact way too daring for its day and the dungeon scene was removed by bastard censors. But it's back now and it's great, if you like that sort of thing of course, which, as you're reading a review of a Franco film, you do.
I love this film.