I had not seen it since then but it lingered in the memory. so its good to see it again now on dvd. Seems this could have been Scorsese's first feature,but he was replaced. It is a bleak tale of a murderous rampage by two seedy killers: the obese nurse and her scuzzy boyfriend (Tony Lo Bianco) as they plot to fleece lonely widows whom he romances and lets them think he is going to marry them, while she, posing as his sister, tags along in the background. Once seen, it is not easily forgotten. The film is made by the marvellous Shirley Stoler (1929-1999) as the malevolent Martha - she also pops up in KLUTE and is terrifying again as that Nazi concentration camp commandant in SEVEN BEAUTIES in 1975 .... (whom prisoner Giancarlo Giannini has to romance in order to survive - we raved about it, at Italian label). Her 40+ credits also include THE DEER HUNTER.
It is not violent by today's torture porn standards, but once seen it is not easily forgotten as we enter than downbeat world of cheap motels and diners. It is Kastle's only credit.