rated PG-13

Director Guy Ritchie doesn’t do anything new with Sherlock Holmes, but that’s OK. Innovation is nearly impossible to come by when you’re dealing with a 120-year-old character. As Holmes says in the novel “The Sign of the Four,” when you’ve eliminated the impossible, whatever remains, however improbable, is the truth. And the truth is that “Sherlock Holmes” is good, but not improbably great.

But it feels like it should be great. Perhaps it’s the century’s worth of baggage associated with the character—the four novels and 56 stories written by Arthur Conan Doyle and the countless film and TV adaptations, literary homages, comic books and everything else that followed. When it comes to Sherlock Holmes, it’s all been done in one way or another, from pitting Holmes and company against occult conspiracies (see Mark Frost’s 1994 novel “The List of Seven,” which finds Conan Doyle and a Holmesian secret agent named Jack Sparks fighting Satanists) to putting the detective in the future (including his appearances in “Star Trek: The Next Generation”).

This time around, it’s Lord Blackwood (Mark Strong), an upper-crust occultist whose seemingly supernatural schemes are whipping London into a frenzy. The case is bedeviling Holmes and Watson, played here with considerable wit and charm by Robert Downey Jr. and Jude Law, respectively. The detective and the doctor bring Blackwood to justice at the beginning of the movie and he’s hanged in short order, only to return from the grave and implement a plan that, according to his taunts, will end the world as Holmes knows it. Meanwhile, Holmes’ former lover Irene Adler (Rachel McAdams), a femme fatal from New Jersey, similarly vexes the detective, though whether she’s working for or against Blackwood is, of course, a mystery.

There are plenty of mysteries for Holmes to solve throughout the movie, but under the direction of Ritchie, he solves just as many quandaries with his fists and other weapons as he does with his intellect. Ritchie (“Snatch,” “Lock, Stock and Two Smoking Barrels”) makes movies about men who live outside the law and spend their time coming up with ways to double- and triple-cross each other. When the various reversals peter out, Ritchie’s characters commence with punching each other and blowing things up. This isn’t a complaint—Ritchie’s films are solidly entertaining, and “Sherlock Holmes” fulfills that promise perfectly.

The movie has plenty of nice elevating touches, though. Robert Downey Jr.’s Holmes is twitchy and cranky, a man whose almost supernatural intellect is tempered by manic behavior, poor social skills and fits of melancholy. Without a case, Holmes is reduced to lolling about his apartment in a stupor, hiding in the dark and testing new chemical compounds on his beleaguered bulldog. Downey attacks the role with his usual charm and cockiness, and his Holmes fits in nicely (though a bit more sweaty and messy) alongside other iterations of the character. It’s also somewhat accurate, as the original Sherlock Holmes stories subtly hint that the great detective may suffer from some sort of mental illness.

Best of all, Holmes is allowed to think. In a few early scenes, usually when Holmes is about to give someone a good thrashing, Ritchie pauses the action and takes us step-by-step through Holmes’ plan—distract the opponent, block a punch, break his jaw, block another punch, crack his ribs, etc.—before speeding up the action and allowing it to come to fruition. (This, too, is accurate—Conan Doyle’s stories made it clear Holmes was well-versed in a variety of fighting styles.) These moments make Holmes’ later deductions seem like the natural outgrowths of a powerful mind and not the sudden pronouncements of a crime-solving robot.

The Holmes-Watson relationship also is fleshed out nicely. Law and Downey work well together, and this chemistry makes their frequent bouts of bickering feel like the natural result of two friends who are both fond of and infuriated by each other. Their dialogue together is snappy, their action scenes are cool and they, too, fit nicely in with the other rogues, cads and lads that populate Ritchie’s films.

And much like Conan Doyle’s original stories, Ritchie’s “Sherlock Holmes” begs for a string of sequels, the foundations for which are laid out in the film’s final moments. All the elements are in place—a good cast, a showy director, and a cracking story—for a near infinite number of future “Sherlock Holmes” movies. They might not be masterpieces, but they’ll all surely be very good, which is sort of an impossible feat all its own.