Obviously, there's a lot more story to the movie than can be written in one short line. Although the movie gets great reviews, I didn't manage to find a way into the story. But it had all the hallmarks - an anti-hero, Veronica Lake, and it's downwards from the first shot on. I felt that there were too many accidents (sitting next to each other on the train, etc) which made the story quite fantasy-like. A bit more straight drama would have been nice.
The most interesting part is Alan Ladd's lead. His portrayal of the killer is quite multi-layered. Maybe the script tried to help him just a bit too much, by having him "save the cat" and "spare the kid". Anyway, he's a bad man with a good heart - and I am actually not quite sure if that was responsible for his downfall. The story to me felt more like the grinding of the cosmic cogs, and by the way crushing the man in a pool of desperation and blood.
The final sequence was quite interesting, too - and I had a strong sense of deja vu, although I didn't manage to remember which film I had seen that.