It's not often a person sees a play that ends differently from performance to performance. But that's the case with Vertigo Theatre's upcoming production of The Mystery of Edwin Drood. Make that 630 possible endings, in fact.

Based on Charles Dickens’s unfinished final novel, it’s being billed as a "solve-it-yourself musical mystery.” Enter novelist, playwright and composer Rupert Holmes. He offers up an unusual way to explore the century-and-a-half-old mystery in which audiences decide what Dickens may have had in mind. Holmes's musical premièred in New York in 1985. It received both critical and audience acclaim. Performed on Broadway, in London's West End and at the Shaw Festival in Ontario, it won five Tony Awards.

Mark Bellamy, artistic director of Vertigo Theatre, is at the helm of Vertigo's production. "It's hard to write a straight version of the novel, because you'd have to come up with an ending," says Bellamy. "Holmes wanted to be true to Dickens, but open enough so he didn't have to come up with an ending on his own.”

Audience members are introduced to the Music Hall Royale, a Victorian musical troupe, on the opening night of their staging of Edwin Drood. For the next two hours, they watch the Music Hall Royale's rendition of Dickens's tale unfold. The story follows Edwin Drood and his uncle, John Jasper, a choirmaster who falls in love with Drood's fiancée, Rosa Bud. She also happens to be Jasper's pupil. Another character, an immigrant from Ceylon, is also vying for her attentions. An opium den madam is also added to the mix of characters. Following a dinner party on Christmas Eve, Drood disappears mysteriously, and questions start mounting. Audience members cast their votes as to the identities of the murderer, the detective-in-disguise and who should be paired as lovers.

With nearly 20 songs sprinkled throughout the show, ranging from ballads to rousing group numbers, music is key to this production. Actors double as musicians, playing instruments ranging from violins to trombones. Bellamy says this is the first time such an approach has been tried.

In keeping with the time, Bellamy incorporated the technology that would have been used in late 19th century theatre. For example, rather than using pre-recorded sound effects, the audience can see the actors operating a wind machine onstage.

With up to 18 performers onstage at once, The Mystery of Edwin Drood is the largest production Vertigo Theatre has ever staged in its 31-year history. The cast features a number of actors well-known to Calgary audiences, including Elinor Holt, Doug McKeag, Tim Koetting and David Lereaney. Onalea Gilbertson takes on the title role, that of a male impersonator who the Music Hall Royale hires to play their Edwin Drood.

"When an audience comes to see a mystery play, they're coming to play a game," says Bellamy. "Well, this one really is a game," he laughs, "as the actors come out into the audience, and audience members actually get to help decide the ending."