Darkness and danger shroud the vexing Mercury Fur, the controversial Philip Ridley play. Still, no one can say that boundary-shoving Who Wants Cake? didn’t know what it was getting into with this production: its promotional materials point to the many patrons who have walked out on other productions, brandishing the fact like a medal. In this staging, director Joe Plambeck shows particular skill at heightening the shock factor by bolstering the show’s emotional core. The result is a play with the potential to turn stomachs and to wither hearts.

The cryptic plot is learn-as-you-go. Brothers Elliot (Jon Ager) and Darren (Nico Ager) break into an empty apartment of a condemned building, at first lit only by their flashlights, and deem it an acceptable locale for the night’s party. Between the content warnings displayed on the theater’s walls and programs and the surroundings, it’s clear whatever they mean by “party” is more nefarious than balloons and cake, but the specifics are unraveled by miniscule degrees only as the other players begin to arrive. The play’s uninterrupted two hours unfold in real time on a wave of maniacal energy, frequently driven by Elliot. With the party bumped up on the schedule by several days, there’s barely time to get ready, and many of the interactions are fueled with getting the preparations on track: cleaning the apartment (a fine wreck of a set by Katie Orwig); collecting the Party Piece (Scott Wilding), some kind of human accessory, to be dressed by the transsexual Lola (Vince Kelley); directing fellow squatter and hanger-on Naz (Alex D. Hill) to perform various grunt functions; and convincing the fearsome ringleader Spinx (Patrick O’Connor Cronin) that everything is proceeding according to plan. Often bickering, always moving, the characters insult each other using strings of unrelated racial slurs; they are all fountains of invective, but little more could be expected from such a band of droogs.

Darren is stoned on something, which turns out to be hallucinogenic butterflies, the recreational drug of choice in this apocalyptic world. He has trouble remembering things — nearly everybody seems to, in fact. With diminished recall and not much to live for in the ruined present, the characters trade stories and history like currency; their accuracy is of little accord, but clear or skewed, these tales develop relationships and slowly unravel the necessary exposition. The two Agers (brothers in real life) embrace the older/younger dichotomy, playing their assigned roles as caretaker and screwup. Hill plays Naz as a ruined cartoon sidekick, obnoxious and terribly endearing in his subservience. Kelley’s Lola is a spectacular presence, on top of her job and her emotions both and knowing just how to wield her influence; an early scene with Elliot shows exceptional tenderness. Cronin is an unimpeachable beast, which he tempers by an unusual attachment to his charge, the Duchess (Cassandra McCarthy). For her part, McCarthy keeps her delighted, delusional character at the edge of hysterics, adding another dangerous variable to what is supposed to be a precise formula. With the success of the party riding on him, Wilding’s unstable Party Piece is a great source of surprise and woozy suspense.

By the time the Party Guest (David Legato) arrives, it seems like things are getting pretty bad. They get worse. Plambeck and company take Ridley’s already-high stakes and make them feel unbearable. What the Party Guest has to reveal is handled with sufficient gravity and wracked emotion to make the viewer long for the isolated depravity of the party. The melee that is the climax is something to be endured; the inaction expected of a live theater audience is turned on its head to make the viewer feel complicit. Legato brings disturbing enthusiasm to his corporate menace; that even these underground savages abhor him is telling. The costume design, also by Kelley, is a smorgasbord of dress-up filth, a credit to the production. Plambeck is lighting and sound designer; the former plays beautifully with light by windows and candles, and the latter features an undercurrent of theremin sounds by Frank J. Hampton, an insistent presence that lends to the overall mood.

Mercury Fur cannot be recommended to everyone. In its capacity to build tension and hold the viewer rapt, it is amazing. It is also amazing how thoroughly it mortifies. This is not necessarily a bad thing; the very fact of the production’s ability to take emotional hostages is proof of the remarkable power of theater. This notably squeamish reviewer might not have chosen to see the show for leisure, but watched it through to the end without looking away. Although forcefully disturbing theater often sends people sprinting either toward or away from it, this is a play whose sway is a direct result of its skill, and its themes and questions are worth the attention of a viewer ready for the onslaught.