Which is worse: feeling pain, or feeling nothing?

That’s one of many questions driving Peter Shaffer’s “Equus,” now playing at the Blackbird Theatre. (Note for those lining up a babysitter: the production runs nearly three hours.)

The Tony-winning drama focuses on a psychiatrist, Martin Dysart (Lee Stille), who’s asked to treat a young man, Alan (Evan Mann), who violently blinded six horses. As trust slowly builds between doctor and patient, the bizarre mystery of Alan’s act is unraveled, and the existential ache at the center of Dysart’s life is exposed.

Per Shaffer’s script, all of the players stay on stage throughout the show, composing a sort of silent, watchful chorus when not involved in the action.

For “Equus,” set designer Barton Bund has shrouded the Sh\aut\ Gallery in black, while curved white piping, like scattered ribs, provide texture and underscore the play’s macabre tone.

And while the tight space occasionally challenges director Sarah Lucas - Alan’s crucial childhood flashback scene seems awkwardly staged, to name one example - she generally does an admirable job harnessing the myriad challenges of “Equus.”

It helps, naturally, that Lucas has a pretty strong cast with which to work. Yes, actors occasionally slipped in and out of their British accents on opening night; but this was a minor issue in a production that grew breathtakingly enthralling as the play progressed.

Of course, the audience’s guide through this dark tale is Dysart, and in that role, Stille anchors the production with powerful authority. Spanning moments of quiet reflection, rage-fueled questioning, and everything in between, Stille provides an arresting, sympathetic portrait of a man who’s thrown into personal crisis while questioning the good served by “curing” the passionate, if pained, Alan.

Mann, meanwhile, took some time to find his footing on opening night, but by the second act, his guts-out commitment to the role (including an extensive nude scene) won me over. Plus, the ensemble deserves accolades of its own, by virtue of its work in individual roles, but also thanks to its uncannily haunting depiction of a stable of stomping, sputtering, ominous horses.

Many elements contribute to these scenes, of course. Bund’s wire frame horse head masks, paired with Luna Alexander’s costumes (complete with trailing skirts of metallic items that sound like rattling chains when the actors move); Emily Clarkson’s atmospheric lighting design; Jennifer Graham’s thoughtful movement/choreography; and the ensemble’s eerily powerful execution all combine to make the stable scenes an intense, all-consuming feast for the senses.

Plus, John Dioro’s affecting, subtle sound design adds subtle chords of emotion to a number of scenes throughout the show.

There are some who believe that the moment for “Equus” has passed; and indeed, a few things in the script feel too “on the nose” (Alan replacing his bedroom poster of a bloodied Christ with a poster of a horse) and over the top (Dysart’s sublimely disturbing nightmare).

Yet nonetheless, my guess is that you’ll be hard-pressed to resist being drawn into Shaffer’s strange mystery all over again - such that wild horses couldn’t drag you away.

Jenn McKee is the entertainment digital journalist for AnnArbor.com. Reach her at jennmckee@annarbor.com or 734-623-2546, and follow her on Twitter @jennmckee.