One of the baser laws of show business maintains that you gotta have a gimmick, kid, if you wanna get ahead.

"The Mystery of Edwin Drood," the latest musical to emerge from Joseph Papp's Public Theater, has one: a last-minute plebiscite, whereby members of the audience are asked to vote on a variety of issues determining the outcome of the plot. And indeed, largely on the novelty of that gimmick, it would appear, "Drood" is pulling the crowds into the Imperial Theatre.

The show by Rupert Holmes is based on the novel Charles Dickens was writing at the time of his death. As one of the cast members euphemistically puts it, Dickens "laid down his pen" before resolving such critical matters as who killed the stalwart Edwin Drood and why. So when the musical reaches the point where the original story gives out, the cast appeals to the audience for help.

The various suspects are lined up on stage -- rather like the finalists in a beauty pageant. By a show of hands, spectators choose the culprit for the evening, whereupon the musical, which is equipped with optional endings, forges on to its climax.

Such democratic principles notwithstanding, "Drood" is the kind of second-rate musical that emerges as a hit mainly because there's nothing else on the horizon. (And Broadway without its yearly musical smash is a panicky place.) "Drood" forces the revelry and italicizes the cleverness -- not so much courting an audience as badgering it into having a good time. The antic spirit proves to be as labored as the grin of a traveling salesman with one foot in the door.

The Victorian sets and costumes for "Drood" are certainly the best money can buy. Nor can you dismiss a cast headed by the ebullient George Rose, as a music hall impresario; jazz singer Cleo Laine, as the proprietor of an opium den; and Betty Buckley, formerly the most downtrodden of "Cats," who here dons male togs and appears as the upstanding Drood. Giving them more than a run for their money is Howard McGillin, who plays Drood's rival in love, a man of the cloth with a crippling fondness for pretty young flesh. (McGillin's performance, my favorite, is a glorious orchestration of false piety and hair-raising lust -- the hair being his, of course.)

The musical doesn't just relate Dickens' story of courtship, treachery and stormy nights in the cathedral city of Cloisterham. Holmes imagines that this saga is being enacted for our edification and delight at the tatty Music Hall Royale by performers who bear a notable resemblance to the hapless thespians of "Noises Off." A brawling, jealous crew, hungry for fame, they see to it that "Drood" is at least as much about 19th-century ham as 19th-century England. Rose, flush with cheer, sets the tone when he welcomes the audience to the Royale, suggesting with a wink that we "all be as vulgar and uncivilized" as we can.

Holmes' songs pretend to come right out of British music hall, and at least one, "Off to the Races," does afford the company a moment of appropriate jauntiness. "Don't Quit While You're Ahead," another ensemble endeavor, manages a near-infectious ring. The rest of the score is not so beguiling on first hearing, however, and belies the rowdy populist spirit the production is trying to whip up. Others have spoken of Holmes' prowess as a lyricist and I would like to believe them. But I found fully 50 percent of the lyrics -- and about 75 percent of a patter song entitled "Ceylon" -- falling prey to the combined evils of overamplification and underarticulation.

Nothing about "Drood" is relaxed or easygoing, although it wants us to roll up our sleeves and slip off our shoes. Director Wilford Leach, who put the pop into the Public Theater's long-running revival of "The Pirates of Penzance," tries to keep things jumping on several fronts at once. But his efforts are reminiscent of a manic juggler who won't content himself with six airborne grapefruit, but insists on adding four rings and two burning torches to the mix. Although choreographer Graciela Daniele is not given many spots to shine, she works with a frenzy when the occasion presents itself. She reprises the rambunctious kick line from "Pirates," and to illustrate the visions in a pipe of opium, concocts a tasteless bacchanal in which chorus girls in tight body stockings slither out of the depths of an unmade bed.

The stars of the Royale company milk the audience for applause, the supernumeraries toss in their two bits from the sidelines, Rose scurries on and off to keep spirits high and the plot more or less on track. And none of it bears a hint of spontaneity, which is the joy of music hall.

Surprisingly, Laine, looking like a puffy Raggedy Ann doll, projects little of the ease she displays in concert, and Buckley is as starchy as her white collar. Jana Schneider, endowing the role of a Ceylonese maiden with a "somewhat strange geographically untraceable accent," darting tongue and exotic undulations, registers as a candidate for a sideshow. No wonder Joe Grifasi impresses as a sad sack yearning for his chance at center stage, but too timid to claim it. Just about everyone else is lunging straight for the bull's-eye.

There is, however, that gimmick to redeem a less than triumphant outing. In the deepest spirit of a musical that seemingly would sell its soul for a Tony, I came to view it as the ultimate calculation. After all, what better way to disarm an audience than to involve it directly in the fortunes of the show? How can you dislike "Drood," when presumably you've had a hand in its making?

The Mystery of Edwin Drood. By Rupert Holmes. Directed by Wilford Leach; choreography by Graciela Daniele; sets, Bob Shaw; costumes, Lindsay W. Davis; lighting, Paul Gallo; musical direction, Michael Starobin. With Betty Buckley, Cleo Laine, George Rose, Patti Cohenour, Howard McGillin, Joe Grifasi, Jana Schneider, George M. Martin, John Herrera. At the Imperial Theatre in New York.