Paradise Found, Menier Chocolate Factory

There's bizarre, and then there's Paradise Found, a new musical that falls so short of the not always clearly defined mark that audiences may likely be mulling over what went wrong for years. What do the two acts have to do with one another? What in heaven's name is the point? How much weight in water is leading man Mandy Patinkin losing per performance?

Those are just a few of the questions spectators will be left pondering during what for many will nonetheless be essential viewing, notwithstanding the show's self-evidently inchoate status. Not in a quarter-century of playgoing this side of the Atlantic have I clocked so many sizeable Broadway talents sharing so small a London stage, in this case south London's seriously ambitious Menier. The entire experience must be an adventure for its cast, just as it's a head-scratcher, and then some, for the audience.

In some ways, this show's willingness to be different is of a piece with the career of its inceptor, Harold Prince, the Broadway titan, now 82. He directed the original Cabaret and collaborated with Stephen Sondheim on a handful of musicals that reshaped the genre (Company and Follies among them), daring audiences to come along on an unexpected journey that, within the parameters of each piece, was theatrically confident and complete in and of itself. The Menier has itself perpetuated that legacy via its ongoing Broadway revival of A Little Night Music, first seen two winters ago in London: a show whose reappraisal at the hands of Trevor Nunn would have been unthinkable without Prince's glistening 1973 original, itself long since the stuff of legend.

And there's a direct musical link between Night Music and Paradise Found in the emphasis on waltz time (Stephen Sondheim there, Johann Strauss II here, albeit adapted and arranged by frequent Sondheim orchestrator Jonathan Tunick), except that the first show, if done well, carries its mixture of sensuality and heartache with glancing wit. By contrast, Paradise Found wants to be funny, I think, as well as sexy and presumably moving in the second act, but it's so conceptually unsure that you feel as if you're watching a prolonged identity crisis in close-up. In the theatre, as with life, that can prove a highly awkward place to be.

Prince and co-director/ choreographer Susan Stroman's source is The Tale of the 1002nd Night, a novel by Joseph Roth, the Austrian writer who essentially drank himself to death in 1939. But whereas Roth's origins - and dates - might seem to land this show somewhere in the Weimar-era landscape of Cabaret, Paradise Found instead tells an often bewildering story of desire that is contingent upon a clash of cultures: the arrival in Vienna during its Austro-Hungarian heyday of Persia's sexually frustrated Shah (John McMartin, an alumnus of the Prince/ Sondheim Follies), accompanied by his self-described "castrate", the Eunuch (played by Mandy Patinkin, whom Prince first brought to attention on Broadway in 1979 as Che in the original American production of Evita).

So far, so, um, unusual. Richard Nelson's book, coupling modern-day colloquialisms like "perhaps you need to get out more" (this spoken by the Eunuch to the Shah) with a Shakespearean bed trick by way of Measure for Measure, is another piece about the dictates of desire that is also, of course, Vienna-based. The Shah, it seems, falls hard for the Empress Elizabeth but ends up in a carnal embrace with a leggy tart and royal look-alike called Mizzi (Kate Baldwin), who says things like, "Excuse my coarseness, Your Majesty" - a comment that seems unnecessary, to put it mildly, given the Shah's penchant for remarking, "I need to see new things," while clutching at a pair of imaginary breasts.

All very faux-Barbara Windsor, you might think, until a second act during which we suddenly hurtle ahead 15 years, with Ellen Fitzhugh's lyrics on hand to remind us, "Vienna is timeless; we live in tableaux." (Huh?) In the intervening period, the bald-pated Eunuch has acquired a head of hair that vaguely suggests what the fluty-voiced Patinkin might look like were he ever to end up in the Menier's smash Broadway transfer of La Cage aux folles (a casting gambit that had in fact been briefly mooted). Mizzi, it seems, has landed in debtors' prison;  Judy Kaye's feisty brothel-keeper Frau Matzner has apparently become a businesswoman par excellence, and the inevitably loud-voiced, lusty Baron (Shuler Hensley) - every period musical needs one of those - descends into drink via some sort of foray into vaudeville. Except, as we're reminded in this musical's closing passages, "theatre is never as interesting as real life".

That's not altogether true when it comes to Paradise Found, which offers the multiple fascinations attendant upon material, like it or not, that at least comes from a place of creative curiosity as opposed to the interchangeable jukebox-driven, film-friendly titles that these days define most of the "new" musicals that open either side of the Atlantic. (Now if only it were funny... )

Watching Patinkin - his eyes closed as is this performer's wont - deliver an ecstatic paean near the end to "the sand dunes (and) palm trees" is to be reminded of the rapture this performer leant all those years ago to Seurat in the first-ever Sunday in the Park with George; onetime Oklahoma! Tony-winner Hensley is no vocal slouch either, nor are a trio of leading ladies extending beyond Baldwin and Kaye to include Nancy Opel, who was Prince's alternate Eva Peron back in the Broadway mists of time. Opel, face barely visible under a pile of blonde curls, looks as if she's having fun sinking into (or bursting out of) Judith Dolan's richly patterned costumes. Beowulf Boritt's design, flanked by reflective glass so as to enlarge the feel of the narrow playing space, at one point introduces a cardboard chandelier, which may be Prince's way of poking fun at what is by light years his biggest hit to date: The Phantom of the Opera, a musical you may have heard of about a chandelier.

Perhaps time, in fact, is the actual topic of a show that makes its own temporal leaps on the way to a weird hymnal finale that suggests Paradise Found as a play about play-making, albeit possessed of a smutty, end-of-the-pier alter ego that drives the first act. Can what is an unabashed out-of-town tryout put the piece right as it heads westward to New York? I couldn't begin to tell you, but I do know this: a major musical's birth pangs can be a mesmerising thing to watch, but only time will tell whether a show set in fin-de-siècle Vienna has, well, reached its fin.

• Paradise Found at the Menier Chocolate Factory until 26 June