What a strange movie. Rife with biblical allusion and a psycho who wouldn't be unfamiliar to the Coen brothers, this is a sort-of Hansel-and-Gretel where the witch is a warlock who comes to them. Robert Mitchum nails his role as the murderous preacher. The black-and-white cinematography is amazing, and directing it must have taken it out of Charles Laughton as he didn't try to do it again.
This was the last of the IMDB top-10 noir movies for me to see. Definitely worth a look, though it doesn't completely hang together (nor separately).