It has become standard operating procedure to envision superheroes as tortured figures, yet no superhero movie has been as doom-laden as The Dark Knight. Oppressive but never overwrought, the movie takes us deep into pop madness. You would think the arrival of the Joker would lighten things up, except that this villain – as envisioned by director Christopher Nolan and portrayed by Heath Ledger – is nothing less than an anarchic sociopath. Ledger performs a delirious, high-wire act. You can see his eyes darting about in each scene looking for a way to unsettle his costars, which he does. Better yet, he unsettles us. Nolan, meanwhile, used Imax cameras for six central sequences, making all the mayhem look majestic. (You almost understand what the Joker gets so excited about.) The Joker may be the picture’s most arresting figure, yet he’s simply a measuring stick for the limits of Batman’s vigilantism. How far will Batman (Christian Bale) go to stop this terrorist? Will the Joker pull him – not to mention district attorney Harvey Dent (Aaron Eckhart), who suffers greatly for being the public face of justice – deeper into madness? Most superhero movies make you slightly envious of the out-of-this-world characters and their powers. After watching The Dark Knight, you’ll be relieved to be normal.