We begin with Stanley with a gun to the back of his head.
You see, Stanley deserves to be in this position. Or at least we're made to believe this, he asked for money from a loan shark (never do this kids, lone sharks are not human), and since he didn't pay back a hitman is sent his way.
This would be the Stranger, a man consumed by darkness and regret, who really doesn't care anymore for his own soul and actually enjoys what he does.
Now, telling you more about this is telling you the full story. What I can tell you is that the fear of loosing your life is quite real in this story.