SHERLOCK HOLMES liked to say that his unique method of investigation was based on the observation of trifles.

The new screen version of the venerable movie staple is based on an observation of its own - that no franchise will nowadays succeed without the enthusiastic support of young males.

And so Holmes (Robert Downey Jr.), before he has a chance to make a single brilliant deduction, is tossed into a bare-knuckle brawl with a hairy heavyweight.

The scene takes us inside Holmes' head, where he uses his big brain to plot out the sequence of athletic maneuvers that will allow him to duck a punch, break the man's knee, crack his rib, puncture his kidney.

It's while watching this that we remember the new "Holmes" is directed by Guy Ritchie, who featured Brad Pitt as a bare-knuckled brawler in "Snatch," and orchestrated all sorts of violent mayhem in his other movies.

Like other Ritchie movies, it's violence with an impish sense of humor, and he may have found the perfect imp in Downey Jr. (as in "Ironman," he turns his diminutive size into an asset).

It's fair to say that in Ritchie's hands, Holmes beats up more bad guys than he outwits - Sherlock Holmes as action hero? In other ways, the movie is soundly in step with classic Arthur Conan Doyle - it favors observation over intuition, science over the supernatural.

The hound of the Baskervilles, you'll recall, was a fictitious dog in a horror story cooked up to provide cover for thoroughly explicable human enterprise.

The same dynamics are at work in Ritchie's "Sherlock." Holmes matches wits with an evil genius (Mark Strong), a purported master of black magic who wants to seize control of a secret society of noblemen, then the empire itself.

Strong (who looks like Basil Rathbone) has made a lucrative career playing stylish villains (see him in "Young Victoria"). He stands as a legitimate rival to Holmes, as does Holmes' famous assistant Watson, played by Jude Law.

Law jettisons Watson's image as intellectually inferior straight man, and plays him as a kind of buddy movie co-equal, a masculine "regular guy" counterpoint to Holmes' eccentric weirdo.

They squabble - Holmes is threatened by Watson's pending marriage, and himself is nearly undone when an old flame (Rachel McAdams) suddenly appears.

You'll have better luck enjoying the performances than following the plot. Everyone seems to be having a nice time, except McAdams, who looks a little lost in the role of femme fatale.

Digital artists are employed to recreate Victorian London, and though you'd think they'd want to restore London to its former glory, their main goal seems to be a monochromatic griminess.