Even before the show opens, the audience is involved. Performers mingle with the patrons in the front rows, talking about “voting” and stuff. Oh God, our civic duty even follows us to the theater. Luckily there is no debate or caucus to sit through, but instead, a thoroughly enjoyable musical in which the audience decides the outcome.

Most mysteries are solved by the end of the book or play. Loose ends are tied up and questions are answered. Sadly, the completion of Charles Dickens’ “The Mystery of Edwin Drood” was interrupted by the untimely death of the author. Though we shall never know what he had in mind for the solution to the mystery, it gave playwright and composer Rupert Holmes the opportunity to create a musical where the ending, or endings, are determined not by the writer, but by the audience.

Calling on the best traditions of English Music Hall — a play within a play, the leading boy played by a woman in drag, and audience participation — Holmes created a theatrical experience which pulls us into the various threads of its story, and asks you the audience to weave them together. Holmes won a clutch of Tony Awards for “Drood,” including Best Musical, Best Original Score and Best Book.

Foothill seems to have accumulated a cast of thousands to populate both the Music Hall Royale theater company and the citizens of Cloisterham, a sleepy English town with its own cathedral. We are directed around the town and its characters by “The Chairman,” who leads the company. John Mannion does an excellent job as he sings “There You Are” with the company. Holmes’ lyrics and book fully deserved Tonys with lines such as “There you are, just west of Leicester Square you are.”

John Jasper (Benjamin Ball) plays the rather devious uncle of young Edwin Drood (principal boy played by principal girl Chloe Angst). Drood is engaged to the lovely Rosa Bud (Brenna Sammon) who happens to take singing lessons from Jasper. He clearly has designs on his nephew’s fiancée and writes her a song — “Moonfall” — which he insists she sing for him (she sings beautifully, by the way).

David Allen / Foothill Music Theatre

Heather Orth as Princess Puffer in "The Mystery of Edwin Drood."

In the subsequent disappearance of Drood, Jasper is Suspect No. 1 and our suspicions are increased when he visits the Opium Den run by Princess Puffer, a wonderful Heather Orth, who puts on her best London accent. She tugs at our heartstrings with “The Wages of Sin,” and insists that the audience help her out with the final refrain — multiple times, as it happens, until she is satisfied with our performance. Jasper partakes of the opium and mixes it with wine, calling out from his stupor “Rosa Bud! Rosa Bud!” (Wait, did Dickens inspire Orson Wells’ “Citizen Kane?”) Back in Cloisterham, two new arrivals appear from Ceylon in the form of brother and sister Neville and Helena Landless, played with suitable Indian charm and also some deviousness by David Murphy and Rachelle Abbey. They join with the townspeople as they sing “A British Subject.” Another great line from Holmes: “Cape Town or Burma, what’s the fuss? All terra firma belongs to us.”

Holmes has many other playwriting and songwriting credits to his name apart from this musical, including the No. 1 platinum song “Escape,” also known as “The Piña Colada Song.” The Gilbert and Sullivan-esque tongue-twister “Both Sides of the Coin,” sung by The Chairman and Jasper, caused much hilarity in the audience as it got faster and faster.

All the characters in the town and the theater company must have created quite a task for the seamstresses. The costumes are all fabulous, with their bustles and bodices, and the Indian garb of Neville and Helena seem thoroughly authentic, at least to a western eye. The Chairman is reminiscent of The Fat Controller from Thomas the Tank Engine.

But in Cloisterham it is Christmas Eve and the weather turns nasty (yes, it was a dark and stormy night), and by the morning Edwin Drood has disappeared, never to be heard of again. Did he die? Was he murdered? Dickens took his own answers to the grave, so the audience is asked to vote for one of a number of possible endings involving not just Drood’s potential killer, but also which pair of characters should fall in love and ride into the sunset. This kind of voting we can cope with, and the results on opening night were somewhat surprising, and hilarious, the actors quite prepared to act out the audience’s chosen ending(s).

Foothill Musical Theatre transports the audience back to 19th century England in a thoroughly enjoyable production. It might not have been quite as Dickens imagined it, but if you come along to “The Mystery of Edwin Drood” without any great expectations, you will be enthralled by the various twists, audience participation and a wonderful theatrical experience.