Murder most musical

Tim Burton makes fantasy movies. Stephen Sondheim writes musicals. It is hard to think of two more optimistic genres of popular art, or of two popular artists who have so systematically subverted that optimism. Sondheim has always gravitated toward the dissonance lurking in hummable tunes, and has threaded his song-and-dance spectaculars with subtexts of anxiety and alienation. Burton, for his part, dwells most naturally (if somewhat uneasily) in the realms of the Gothic and the grotesque, turning comic books and children's tales into scary, nightmarish shadow plays.

And so it should not be surprising that Sweeney Todd: The Demon Barber of Fleet Street, Burton's film adaptation of the musical, is as dark and terrifying as any motion picture in recent memory, not excluding the bloody installments in the Saw franchise. Indeed, Sweeney Todd is as much a horror film as a musical: It is cruel in its effects and radical in its misanthropy, expressing a breathtakingly, rigorously pessimistic view of human nature. It is also something close to a masterpiece, a work of extreme - I am tempted to say evil - genius.

As it was originally performed onstage, with all the songs Sondheim composed for it, Sweeney Todd balanced its inherent grisliness with a whimsical vitality. The basic story is a revenger's tragedy more Jacobean than Victorian, but Sondheim nonetheless wrings some grim, boisterous comedy out of both the impulse for vengeance and the bustling spirit of commerce. A barber, wronged by a powerful judge, returns to London and sets up shop, cutting throats as well as hair. The bodies of his victims are turned into savory meat pies by Mrs Lovett, his energetic partner in business and crime. Cannibalism and mass murder: The basis for a hit show.

It seemed a lot less funny in the recent revival, which starred Michael Cerveris and Patti Lupone in roles originated on Broadway by Len Cariou and Angela Lansbury in 1979. Burton's film, in spite of the participation of Sacha Baron Cohen (as a mountebank barber in a skin-tight costume) and Timothy Spall (as a louche bailiff) pretty much casts out frivolity altogether. Burton's London is a dark, smoky oil slick of a city. Dante Ferretti's production design, which owes something to the Victorian city confected for Carol Reed's Oliver!, can make even daylight look sinister. Innocence, represented by a pair of young would-be lovers (Jayne Wisener and Jamie Campbell Bower) has virtually no chance in this place; it is a joke played by fate, something to be corrupted, imprisoned or destroyed.

Lovett the pie maker is played by Helena Bonham Carter, a witchy fixture of Burton's cinematic universe as well as the mother of his children. If the director has an alter ego, or at least an actor consistently able to embody his ideas onscreen, it would have to be Johnny Depp. He was the hurt, misunderstood man-child in Edward Scissorhands, the cracked visionary in Ed Wood and the cold, creepy candy mogul in Charlie and the Chocolate Factory, in each case giving form to an emotional equation that had never quite been seen on film before. As Sweeney, his hair streaked with white and his eyes rimmed in black, he is an avatar of rage.

Depp's singing voice is harsh and thin, but amazingly forceful. He brings the unpolished urgency of rock 'n' roll to an idiom accustomed to more refinement, and in doing so awakens the violence of Sondheim's lyrics and melodies. Some of the crowd-pleasing numbers, like The Ballad of Sweeney Todd, have been pared away, but their absence only contributes to the diabolical coherence of the film, which moves with a furious momentum toward its sanguinary conclusion.