Certain people have issues to escape what they are doing. And even if they manage to do so, most of the times they will leave something behind they urge to get back (to). It's the thing that one is supposed to evade (see De Niro in Heat, though he didn't really listen to his own advice either). In this case it is not even the strong wish of the main character to get back ... but an unfortunate "incident" that makes it impossible for him to stay away.
And while he is on the verge and on the lookout (or on a mission or however you want to call it), there is a different danger lurking! Actually not so much lurking rather than sprinting and running towards him. And this nemesis of his, who is seemingly unstoppable, makes this movie quite the experience. By the way the action and stunt work on this movie ... just wow! Incredible to say the least! Just for that this is worth watching, if you are into that sort of thing of course