When a flashback to happier days begins, the glare of full, sunny color almost hurts the eyes.

It's then, perhaps, one realizes just how dreary and dark Tim Burton's London lies waiting in Sweeney Todd: The Demon Barber of Fleet Street, a Stephen Sondheim musical brought to the screen in incredibly gory glory. The casual eye is almost fooled into thinking the film is black and white, but the startling lack of color is deceptive; there's just enough hints and hues to add depth and richness to the grays, blacks and blues that dominate the screen.

The city in which the story is set is full of soot and stark shadows, a moody gloom that presages the doom to follow. For Sweeney Todd is back in town, and his silver razors (surprisingly untarnished after 15 years in a box under the floorboards) have made his arm complete once more.

And blood -- thick and plentiful -- is often the only splash of color on the screen ... and man, does it splash! It splashes and runs and pours and drips and clots in the most amazing ways, more arterial spray than artistic display.

Sweeney Todd, we learn, was once a young and simple man in love. But his beautiful wife drew the attention of the powerful and ruthless Judge Turpin (Alan Rickman), who has the young barber arrested and transported to Australia for a nonexistent crime. Todd's bride, Lucy, drinks arsenic to escape Turpin's lust, so the judge takes in the couple's young child and, with infinite patience and dreadful perversity, assumes she will eventually mature into her mother's equal in beauty.

She does, enough to draw the eye of a young sailor who hopes to free her from the judge's clutches. But that lucky romance is secondary to Todd's dramatic return to London, where he concocts a foul partnership with down-on-her-luck pie-maker Mrs. Lovett to take his revenge on all who have wronged him -- and anyone else who might take a seat in his barber's chair. Todd doesn't get a lot of repeat customers.

Johnny Depp, who in his sixth collaboration with Burton seems custom-made to star in this film, has a handle on the madness and rage that drives Todd through this murky plot. He glowers and rants and stalks through the streets of London like a force of nature carved right out of a stormy and unforgiving sky.

As Lovett, Helena Bonham Carter provides some of the film's lighter moments, for all her butchery and barbaric baking. She boasts of making the worst pies in London (although the roaches seem to like them) and sings of a bright and happy future by the sea that is, of course, rather unlikely. Meanwhile, she drifts through the story a splendid icon of tired beauty, rough and soiled and yearning for love.

She and Depp are both beings of pale skin and wild hair and dark circles hiding wide and staring eyes. It is impossible not to be creeped out by them, even when their hands are clean and unbloodied.

Burton had all the right ideas for making this film. Besides perfect casting and setting, he chose well when deciding to use actors, not singers, in this musical production. Depp, Carter, Rickman and the rest might at times exhibit more enthusiasm than polish in their singing, but their performances are gripping and sincere and somehow better for the roughness of their voices. The camera work is brilliant, at times with layers of detail hovering just outside of focus, and there are just enough touches of whimsy to prevent the story from collapsing under the weight of its own moroseness.

Sweeney Todd is part dramatic horror, part black comedy and, of course, a well-crafted musical. But it's also a macabre tragedy, and its final tableau must bring a lump to your throat that tastes only faintly of Lovett's savory pies.