Leave it to Christopher Nolan, mastermind of plots-within-plots, narrative loops-within-narrative loops, to create a middle movie for his Batman trilogy that both worked on its own and as the transition from Batman Begins to The Dark Knight Rises. All three movies explore the nature of vigilantism, of what it really means to take the law into your own hands. Dark Knight offers a deeper exploration of the theme than its predecessor, and that exploration probes even deeper in the final film. (Dark Knight also improves on Batman Begins by replacing Katie Holmes with Maggie Gyllenhaal as Rachel Dawes, Bruce Wayne’s love interest.)
Of course, what really makes the film work is Heath Ledger’s indelible performance as the Joker. Bane (in the third film) may be a stronger opponent, but no one gets into Batman’s head the way the Joker does. With his eerily calm manner, he forces Batman to reckon with a philosophical conundrum: can he defeat the Joker without becoming like him and embracing chaos and anarchy? Or, to put it in terms that haunt Batman throughout the trilogy: can he fight evil from outside the law without losing his soul?