The fact is, Nolan had only found his way to the Batman franchise because it was a distressed asset. After distinguishing himself with neo-noir crime dramas such as Memento and Insomnia, Nolan was handed the keys to the character by Warner Bros., years after the financial failure of 1997's Batman & Robin. Nolan's 2005 reboot, Batman Begins, was well received and a solid box-office hit, but nothing on the scale of The Dark Knight, which made almost three times as much worldwide. The film was so beloved that its Best Picture Oscar snub led to public outcry, which in turn prompted the Academy to widen its nomination field to 10 films the next year.

The Dark Knight legitimized comic-book movies—not with audiences (who, after all, made the original Batman a huge success in 1989), but with studios. In a way, superheroes in cinema have always followed trends set by the Batman franchise. The throwback, Gothic feel of Tim Burton's 1989 film inspired the revival of goofier vintage properties such as Dick Tracy, The Shadow, and The Phantom in the 1990s, while Marvel's more modern characters were ignored. The failure of the supremely garish Batman & Robin convinced studios to hire more acclaimed directors for future projects, such as Sam Raimi for Spider-Man, Bryan Singer for X-Men, and Nolan. And finally, the triumph of The Dark Knight transformed a non-prestige genre into a key part of every studio's strategy moving forward.

While Batman Begins had one foot firmly planted in the pulpier side of the character, The Dark Knight was filmed like a gritty, atmospheric crime movie, with Nolan taking visual cues from Michael Mann's bank-robber epic Heat. Rather than heightening Gotham City to the point that a man dressed as a bat makes sense as its public defender, Nolan turns Batman (Christian Bale) and the Joker (Heath Ledger) into jarring archetypes who are incongruous to the world of gangsters and cops around them, and symptoms of an increasingly polarized society of heroes and villains.

Part of Batman's quest in The Dark Knight is to push the attorney general Harvey Dent (Aaron Eckhart) as Gotham's hero of the future, an effort that implodes when the Joker attacks and scars Dent, turning him into the monstrous villain Two-Face. Most comic-book antagonists have specific motives of world domination or personal revenge. But Nolan presents the Joker more as an elemental agent of chaos—one who's interested only in upsetting the natural order of things wherever he goes, and who's fascinated with Batman because he represents the opposite extreme. It's a vision of evil as something trollish, amoral, and anarchic. "Some men just want to watch the world burn," says Batman's reliable butler, Alfred (Michael Caine)—a line that became an online refrain in the lead-up to the 2016 presidential election.