Sherlock Holmes is one of the great characters: impossibly Byronic, with his superior intelligence and (apparent) imperviousness to the fairer sex; impossibly misanthropic, with his disdain for almost everyone in the world but his amanuensis, Watson; impossibly brilliant, with his near-psychic ability to pin down the past, present, and sometimes future of total strangers based merely on the state of their wardrobe. Sir Arthur Conan Doyle couldn’t have known it, but the chilly remove and observational distance he embedded in Holmes’ literary DNA makes him the perfect wireframe over which almost any story can be overlain, with his serial stories, the first action franchise.

Conan Doyle might well love what Guy Ritchie has done with the world’s first consulting detective: Sherlock Holmes is a much greater departure from Ritchie’s cinematic past, which tends toward tongue-in-cheek depictions of modern urban criminals, than from the Holmes of Conan Doyle’s stories. Purists will moan, but Holmes’ spirit is thoroughly intact in this dynamic, vigorous adaptation. This Holmes is nerdy enough to be respectful to the beloved source material but geeky enough to express its affection the only way geeks know how: with winking snark and post-postmodern metacommentary.

But not a lot of that, either. The suggestion of steampunk – the aggressively science fiction-esque perspective on the Victorian era that contemporary fantasy often takes – remains just a suggestion. The hints that Harry Potter had more than a passing influence on this film remain only hints. Most of what feels modern here is in how the story is told, rather than in the story itself.

So this Holmes – the script is by Michael Robert Johnson, Anthony Peckham, Simon Kinberg, and Lionel Wigram – opens mid-escapade, à la Indiana Jones: We’re thrown right into the fray, the narrative and the relationships of the characters. There’s no setup: You sink or swim as you navigate what turns out to be something of a collapse of the partnership between Holmes (Robert Downey Jr.) and Watson (Jude Law), the latter about to move out of their digs at 221b Baker Street to get married. You’re left to wonder, for the most part, what the deal is with Irene Adler, the slightly shady but very classy American (Rachel McAdams) Holmes has clearly crossed paths with before – what small knowledge about her readers of Conan Doyle bring with them into the theater won’t quite suffice to explain all. You’ve seen the trailer: sex and alcohol are clearly involved.

I remind any objectors to the nature of the relationship between Holmes and Adler that plenty of other players in Conan Doyle’s sandbox have filled in gaps that the author left open. Manly W. Wellman and Wade Wellman, in their 1975 novel Sherlock Holmes’ War of the Worlds, posited that Holmes was shacked up with his housekeeper, Mrs. Hudson, a beautiful young widow. Conan Doyle never said she was a kindly old lady – we all just assumed that.

Holmes is a slob? Did Conan Doyle say he wasn’t? Watson is a true partner to the great, brilliant detective? Conan Doyle’s Watson is a medical doctor and a war hero. Both Downey Jr. and Law are having fun here with such iconic characters, but they’re having it in ways that are both uniquely their own – it must be hard to defy the decades of tradition Holmes and Watson come laden with, even if those traditions were the inventions of previous interpreters of Conan – and perfectly faithful, in their own way. (Downey plays Holmes, for instance, as lonely, and about to get lonelier as Watson pulls away from him, but too stubborn to admit it… and maybe the Watson who “wrote” those original Holmes stories was too obtuse to notice that his friend’s seclusion wasn’t necessarily voluntary.)

The story – about a nefarious lord (Mark Strong) who wants to bring a peculiar brand of religious fundamentalism to bear in the British government – is not something Conan Doyle ever invented, but it’s not unlikely that it could have been. With its combination of a little magic, a dash of wit, and a lot of action, it seems well suited for the “everything’s in transition” feeling to this Holmes and Watson, and to the early 21st century world into which this interpretation comes. How much more perfect could it be?

SHERLOCK HOLMES (3½) Directed by Guy Ritchie • Starring Robert Downey Jr., Jude Law, Rachel McAdams • Rated PG-13 • 128 min. • At Del Monte Cinemas, Maya Cinemas.