One of the most intriguing questions about theater is: What makes it work? A poetic script? Talented actors? Dynamic directing? Intriguing sets, lights, costumes, background music? Or the audience’s willingness to believe?

It was hard to know which of these factors was more at work last Thursday at the preview of “Dracula,” Penobscot Theatre Company’s hauntingly frightful season opener playing through Oct. 3 at the Bangor Opera House. Director Mark Torres adapted the script from Bram Stoker’s 1897 novel, and much of the action for the two-hour-plus production is explained in letters, diary entries and newspaper reports read from the stage. If you’ve seen Torres’ adaptations of “A Christmas Carol,” a standard during the holiday season, then you’re familiar with the presentational style.

Other scenes are played out in traditional dramatic fashion on the cavernous Opera House stage with a backdrop of the building’s original stone work, skeletal wooden catwalks and the equipment of stagecraft peeking from the wings. The last time Torres similarly used the unadorned stage was for his memorable production of “Angels in America,” but this time, the Opera House’s jagged walls and ancient echoes are creepy. If water were eerily dripping to the floor and a few bats were to fly through, the production couldn’t be any more chilling.

From the first growling tones, the production prepares the audience for a story that springs from some of our most wicked nightmares – and it treats the plot with utter believability. You can nearly hear the hearts that beat with fear and the one other heart that beats with hunger.

Part of this is the textured sophistication of Lynne Chase’s lighting design and the moody music and sound effects by Samuel Kuykendall. But the cast is uniformly good, too, and the actors have clearly understood Torres’ approach to a kind of naturalistic melodrama. They move from Transylvania to England, to tombs, sitting parlors, mental asylums, ship decks and sleeping quarters with the help of very few set pieces. They transform from carefree young lovers to devils, from ordinary members of society to superheroes.

The most compelling performance comes from Adam Kuykendall, a veteran performer and director at the Opera House. As with most of the cast members, he plays several roles: a Texan, a sailor, a zoo keeper and Renfield, a mental patient who favors house flies as snacks. As Renfield, Kuykendall evokes the spirit of a couple of famous madmen in cinematic history, but he also brings something entirely his own to the role. It’s a tour de force. Be prepared to wince. But it’s worth noting that his sound and fury actually do signify something important.

In a role that could easily devolve into silliness, Jenny Bragdon, as Lucy, the first woman to be bitten, goes from being girlish and shy – the vignette about her suitors is entirely sweet – to being powerfully dangerous and wicked. Her transformation happens incrementally. So there’s no surprise, but there is still breath-stopping suspense.

These two performers are worth singling out for their individual characterizations, but Daniel Noel, as Van Helsing, Kae Cooney as Mina, Christopher Franklin as Arthur, Chuck Novatka as Jonathan, and Andrew B. Towler as Seward, work as a finely-tuned ensemble that establishes a sense of serious drama from the start.

It helps, too, that Count Dracula is played with elegance and subtlety by Alex Cherington. He’s a Dracula of intellectual grace and charm, and, if anything, he isn’t onstage enough and his scenes aren’t as passionate as one might expect for a story that has all sorts of sexual undertones. Still, his Count looms large in the shadows.

Although it may seem simple from the starkness of the set, this is a complicated show technically. During the preview on Thursday, the balance between the hollow stage, the actors’ volume and ranging accents, and the soundtrack was still being adjusted. On Saturday, stage manager Meredith Perry, whose intense work backstage guides this production smoothly, said the cast and crew had been fine-tuning the sound levels right up to opening night. She assured me that careful improvements have made the show easier to hear. Nevertheless, the seats in the front rows are likely to be the best bet for enjoying this show in all its gory glory. Even better, familiarize yourself with Stoker’s original novel. It’s a long read, but it’s a worthwhile work of classic fiction, and it may help you sort out a few of the characters and plot twists.

In the end, it’s hard to say what propels this production of “Dracula” to – shall we say? – gnaw at the imagination of the audience. Despite the difficulty hearing the actors’ lines during the preview, the audience was rapt. What makes theater work? It may be this simple: When the lights go down, you have a good time. Or – shall we also say? – a deliciously frightening time.

Penobscot Theatre Company will present “Dracula” through Oct. 3 at the Bangor Opera House, 131 Main St. For information or tickets, call 942-3333. Alicia Anstead can be reached at 990-8266 and aanstead@bangordailynews.net.