Pegasus Theatre’s Living Black & White production has become as much a holiday season tradition as A Christmas Carol or The Nutcracker, and like those, it relies heavily on the familiar: The characters you’ve grown fond of, the emotional reaction you’ve come to expect. Unlike those, however, Pegasus can mix up the show every season, with new settings, new casts, new plots. (Who would want to see Xmas Carol without Tiny Tim, or set on Mars in 2121?)

That’s its blessing and its curse: It allows Pegasus’ artistic director, playwright and leading actor,Kurt Kleinmann — who always plays clueless gumshoe Harry Hunsacker — flexibility, but it also makes each show a crap-shoot: Will it be as good as last year?

This year’s production, The Frequency of Death!, is better … at least in Act 1, which has a high percentage of laughs, some hilarious performances and a setting — the studio a 1930s-era radio drama — that permits a variety of action.

Harry and his long-standing assistant Nigel (Ben Bryant) have been asked to serve as panelists on a radio show where a real mystery is acted out and they are the detectives there to solve it. The show itself is a mess — the pet project of the station’s owner, Mr Killian (Gordon Fox), whose business is built on a disgusting sounding “ironized coffee.” Killian insists the director use Miriam (Susan Mansur), a drunken old actress he’s in love with, even though her performances ruin each episode. There is a sound man with a past, an engineer who has the acting bug, an ingenue in competition with Miriam… in short, a motley cast, any of whom might have a motive to murder any of the others.

The star of the show — in aggressiveness at stealing scenes, if nothing else — is Mansur, whose boozy, over-the-top performance is a hoot and a half. Part Angela Lansbury, part Carol Burnett’s Norma Desmond and with a hint of who Kim Cattrall might become one day, her fearless scenery chewing is endlessly watchable. Bryant, looking like a a piece of granite carved to look like Clark Kent, adds a stolid dignity to everything.

And then, of course, there is the effect: The black and white makeup, lighting and sets the nearly flawless take you into the magic world of a pre-Technicolor movie. (Director Bob Bartley even has an inspired opening bit, confining the first scene to an aspect ratio of an old-style movie before opening it up a few minutes later.)

Frequency still suffers from some of the shortfalls of most Pegasus productions: Second act twists that tax credibility (truly of the deus ex machina variety — a villain with the mystical ability to change appearance at the drop of a hat), a solution that seems completely manufactured, too much explanatory dialogue to justify the convoluted mystery, and the annoying antics of Hunsacker’s nemesis, Lt. Foster. And some of the actors lack the precise comic timing to sell the jokes. But B&W show have never been about the destination, but the journey. And this one skips along pretty enjoyably.