The big difference between a murder mystery and a thriller is the amount of time that your hero and villain are openly confronting each other. In a mystery, the villain keeps a low profile and there’s usually not a confrontation until the very end. In a thriller, the thrills have to start by about 30 minutes in, so by that point the hero and the villain usually have an open antagonism.
So why isn’t the movie over ten minutes later?
The answer is the that the hero and villain confront each other, then take some time off, then confront each other again, then cool off some more, then finally gather for their final showdown. Sometimes, in more ambiguous thrillers, this wavering makes sense, but just as often, both hero and villain know right away that only one of them can remain standing, so why do they keep disengaging? Why don’t they finish each other off the first time?
The most famous example of this, of course, is Hamlet. Why does Hamlet delay? There are several reasons given in the plot: First he wants to get more evidence, then he has religious doubts, then he spends two acts extricating himself from an elaborate death trap. But ultimately, Shakespeare never really explains it, so this is considered to be the key question that the director and actor must answer for themselves.
But ultimately we trust Shakespeare, so we give him the benefit of the doubt. If we can’t find enough justification for Hamlet’s delay in the text, then it must be our fault. But we don’t give as much leeway to the people who write Batman comics, who face this problem month after month. In almost every single issue, Batman confronts the villain inconclusively a few times before they finally have it out. And this is the hardest thing for me about writing thrillers: How do you get out of these early action scenes in inconclusive ways? Why would either side walk away without killing or arresting the other? I’ll tell you how: you write a bunch of scenes like this one, from Detective Comics #437:
I myself have written variations on this scene: “Villain throws hero out of a window, can’t check to see if he’s dead, villain is gone before the hero comes back.” It’s better than “Villain puts hero in a death trap, assumes that it works, doesn’t bother to check.” But it only buys you a little time until you have to write your next inconclusive confrontation.