I'm not really sure if this merits as an overlooked movie, since it's quite of a cult classic. Leonard Kastle's The Honeymoon Killers from 1969 is what's usually called a "sleeper", a film whose status has grown over the years, a film that pretty much went by everyone during its initial release. And it's also a film whose status really deserves that growth: it's an excellent crime film with lots of dark overtones and with an artistic touch that makes it stand out amongst its contemporaries.
The story's about the real case of Raymond Fernandez and Martha Beck, two unlikely lovers who got each other mixed up in a scam of marrying stupid elderly women and ending up in killing them. It's an ugly story and Kastle doesn't shy away from it. He gives no clues as to what drives these two people, which makes the movie even more chilling. Kastle denies the easy identification from the viewers. This is intensified by a rather Godardesque use of music - Gustav Mahler whom Kastle admired very much.
The film is shot in murky black and white, some of the set pieces are pretty clumsy, but there's also some great photography and mise-en-scène. Kastle shines out the best as a director of actors: all of them give marvellous examples of great acting. The script must've given them plenty to work with, since the characters are full-blown human beings, even in short sequences - they are not caricatures. It makes The Honeymoon Killers touching and very humane at heart, even though on the surface it's a ruthless story about two ruthless - and rather clueless - killers. But I really, really love Shirley Stoler and Tony Lo Bianco in this. Marvellous! Excellent! And ahead of their time, I should say. You didn't see this kind of acting in Hollywood films in the late sixties.
Highly recommended, if you ever run across it. More Overlooked Movies at Todd Mason's blog.