His name may not mean much as you settle into your seat for the Wolf Trap Opera Company's production of "Sweeney Todd," but make no mistake: Once the lights go down, you'll be deeply grateful for your new acquaintance with Matt Boehler. He is quite simply a marvel as Sweeney, the demon barber of Fleet Street, which is not to say his skills lie anywhere close to the category of depraved indifference.

No, Boehler's license to slay derives from a killer voice box. Imposingly tall and possessed of a supple, clarion bass, the young singer delivers a thrillingly expressive performance in Stephen Sondheim's musical about a cruelly mistreated barber who takes his hideous revenge via the carotid arteries of his unsuspecting clientele.

Boehler strides briskly onto the stage, hollow eyes blazing -- this Sweeney has a job to do -- and walks off with the show. It's such a captivating piece of work that it succeeds in ironing over some of the kinks in Joe Banno's production. Some, that is, but not all. Audrey Babcock's portrayal of Mrs. Lovett, the brazen purveyor of meat pies who cozies up to a homicidal maniac, is underwhelming; her acting abilities fall far below what's required. And the 20th-century setting that Banno devises -- the musical, originally set in 19th-century London, takes place in something like a modern meatpacking plant -- mutes the terror of the piece. The show is not easily guided, it appears, outside the boundaries defined by Sondheim and book writer Hugh Wheeler.

The vigor of Banno's production, however, is unassailable. If opera's claims on Sondheim often feel like poaching, the voices on the indoor stage of the Barns at Wolf Trap provide evidence of just the opposite. These singers make the piece their own. As sung by Boehler and Jason Hardy's Judge Turpin, the magnificent "Pretty Women" has rarely sounded as richly blended. Boehler's sensitive version of "My Friends," Sweeney's love song to his razors, elicits goose bumps, even tears, and the emotional spikes in Alexander Tall's "Johanna" invest that moving number with all the passion and urgency it demands.

Banno, who directs both opera and theater, understands that crisply articulating the lyrics of a Sondheim score is an imperative, and much of the cast rises to the challenge. The 26-piece orchestra conducted by James Lowe makes for a pleasing partner in the proceedings, even if it occasionally overpowers the singers. The acoustical conditions are not ideal for a character-driven song with dense lyrics, such as Mrs. Lovett's "The Worst Pies in London." And though you want to savor every play on words in "A Little Priest," the duet between Sweeney and Mrs. Lovett that sends audiences out for intermission on a cushion of bliss, Babcock undercuts much of the song's humor. She's at war with her own performance, shifting her focus so insecurely, from the spectators to the actors and back again, that she plays convincingly to neither.

Shot through with Sondheim's macabre sense of humor, "Sweeney Todd" is that oddity in American musical theater, a show that intentionally leaves blood on the floor. It's Grand Guignol by way of the music hall, and it seems to work best when you feel perversely protective about the eminently practical Mrs. Lovett, who discovers the profit margin in cannibalism. At the climax of the dazzling Broadway original in 1979, when Len Cariou's seething Sweeney waltzed Angela Lansbury's daft Mrs. Lovett into her own oven, you watched as Lansbury's features melted in horror, and you left the theater in a state of shock. Such was the shrilly disturbing impact of the early Industrial Age as evoked by director Hal Prince.

While Wolf Trap's "Sweeney" lacks some of the original's texture, the show manages to breathe freshly. Part of this is attributable to Banno's encouragement of the performers to explore character as energetically as technique, and part to the sheer vitality of the cast. (Jason Ferrante's prissy Beadle and Javier Abreu's ardent Tobias are among the livelier creations.) The physical environment is a departure from most productions. In this case, designer Erhard Rom conjures a warehouse of contemporary dimensions, with meat hooks suspended from the ceiling and a corrugated steel garage door that conceals Sweeney's ghoulishly sterile shop.

The conceit needs further refinement. The characters, who converse with the formality of a bygone age and ply trades anchored in yesteryear, enter and exit through modern-looking office doors. (Nothing is illuminated in "Sweeney Todd" by trying to make it timeless.) The geography of the staging seems to be based on a map of precious little coherence, with random characters and chorus members appearing in windows for no other purpose than variety.

Banno does, however, judiciously trim the musical contest between Sweeney and another barber, Pirelli (the vivacious tenor Nicholas Phan), a scene that ordinarily becomes labored. And late in the show he adds, beneficially, a rarely used song fragment for the Beggar Woman (Hanan Alattar) that ties her more substantively to the story's terrible ending.

The director's most successful stroke, however, came on the day the rehearsal pianist plunked the first note and Boehler was there to sing it. A mere lad by the middle-age standard for the role, he nevertheless conveys Sweeney in all his ferocious self-absorption. There are times, in fact, when this young man with a big crossover career ahead of him is standing in a crowd of actors, and you'd swear he was the only person onstage.

Sweeney Todd, music and lyrics by Stephen Sondheim; book by Hugh Wheeler. Directed by Joe Banno. Conductor, James Lowe; costumes, Timm Burrow; lighting, Nancy Schertler; chorus master, Bruce Stasyna. With Maureen McKay, David T. Grimes, J. Alan Garcia, Michael Nansel. Approximately 3 hours. Through Sunday at the Barns at Wolf Trap. Call 800-955-5566. All shows sold out, but check for last-minute availability.

The Wolf Trap Opera Company's updated production stars Matt Boehler as the singing serial killer.