Mack the Knife is cutting through the audience. There’s real danger there, not least because the slashing killer from “The Threepenny Opera” may lash out at you as he climbs the stairs of the Southern Theater.

As played by the prodigiously gifted Bradley Greenwald, Macheath, as he is formally known, is an ice-cold killer with a gorgeous voice in the Frank Theatre revival that opened Friday. Don’t be too taken in by his charms, however. This codpiece-wearing don of the Victorian underworld is quick to take a knife to an underling’s throat just to prove a point. He also uses women for sex and hoped-for salvation.

Director Wendy Knox’s staging of Kurt Weill and Bertolt Brecht’s musical cannot be faulted for being too safe or too clean — complaints that critics have made about choreographer Martha Clarke’s current New York version (co-starring Twin Cities-bred actor Laura Osnes). Knox’s production is a thing of strange beauty, with heavenly voices, a recitative that dawdles a little toward the end of the first act and a look that suggests scenes from a nether dream.

“Threepenny” tells a gangland story involving Mack’s secret marriage to Polly Peachum (Suzie Juul), daughter of the exploitative king of the beggars in Victorian England. Mr. Peachum (Gary Briggle) wants Mack’s head, but there’s a problem. Mack and police chief Tiger Brown (James Ramlet) are old chummy friends. So the Peachums (Janis Hardy plays Mrs. P.) hatch a plot to ensnare Mack, who keeps the lines of communication open with his longtime prostitute Jenny (Molly Sue McDonald) and with Lucy Brown (Kira Lace Hawkins), Tiger’s daughter.

The corrupt milieu represented onstage extends from characters such as Crook-Finger Jake (Grant Sorenson), Bob the Saw (James Rodriguez) and Charles Filch (ShaVunda Horsley) to the chock-a-block set pieces (Joe Stanley’s evocative scenic design) and garish garments (Kathy Kohl costumes).

Though sometimes underlit, Knox’s “Threepenny” is notable for the sheer assembly of vocal talent, all under the proficient musical direction of Sonja Thompson. Highlights include the “Jealousy Duet,” a startlingly gorgeous number by Juul and Lace Hawkins outside Mack’s prison cell. The two women’s voices interlace like two birds whose spiraling flight could be for fighting or courtship.

“The Tango Ballad,” by Greenwald and McDonald, is sweet and telling, while Vern Sutton, who plays the Messenger, delivers “Mack the Knife” with confidence and aplomb.

If there is a main drawback to Knox’s “Threepenny,” which runs for three hours, it is that it sometimes takes too long to get to the music.

While Brecht and Weill were ahead of their time in sending up conventions with “Threepenny,” they were still of their age. A number such as “The Cannon Song,” a jaunty duet between Greenwald’s Macheath and Ramlet’s Tiger Brown, is disturbingly backward to modern ears.