Leading a cast of nearly 200, Wallace Shawn has turned his chilling 1990 solo show “The Fever” into an epic portrait of modern-day class guilt. And director Scott Elliott has managed this while still paying only one salary. Using nothing more than a few flights of champagne and the promise of proximity to that guy from “The Princess Bride,” Messrs. Shawn and Elliott have introduced a fleet of extras to their daring evisceration of Western pieties. This willing — if increasingly uncomfortable — cohort is also known as the audience.

“The Fever” begins and ends in the hotel room of a blighted Third World nation, where Mr. Shawn’s narrator lies violently ill, buffeted by waves of shame and revulsion at the suffering he has witnessed. The character is identified only as the Traveler, and as he quickly explains, he has arrived at this miserable (and unnamed) country from the rarefied confines of upperclass Manhattan society. As Mr. Shawn spends the next 100 minutes trying to reconcile these two worlds — and drawing some unsettling conclusions in the process — he steadily confirms his reputation as a devastatingly subversive playwright.

This process, like so many uncomfortable discussions, is cushioned by booze. About 30 minutes before “The Fever” begins in earnest, a nattily dressed Mr. Shawn stands in front of dozens of champagne glasses. A makeshift cocktail party is soon under way onstage, the sort of party at which the Traveler has spent many evenings honing his logically sound, morally damnable theories. While tentatively milling around on Derek McLane’s witty set (a thin slice of a moneyed Manhattan apartment) and semi-subtly craning their necks to hear Mr. Shawn’s conversations, the theatergoers at a recent performance also indulged in plenty of their own chat:

“Oh, come on, like the medical examiner has any idea …”

“We basically help businesses understand where they are and where they ought to be.”

“No, that’s great to know — I’ll download it tomorrow!”

Mr. Shawn, meanwhile, is telling one audience member that he’s nervous about speaking to all these people but also looking forward to it. Has the play begun for him? Does our involvement in this chattering-class soiree somehow implicate us in the excoriating defense of supply-side morality that follows, one in which reparations for the dispossessed are coupled with the sanctioned rape and torture of certain have-nots? Is he in character already? Are we?

The narrator caroms between intense political engagement and equally vehement obtuseness during his travels: “There were lots of soldiers, that’s a fact, but to me they looked more like shepherds in Renaissance paintings.” One could argue that the Traveler’s well-intentioned, philosophically meandering solipsism is appropriate to the character — he shifts from staring at photographs of torture victims to remembering childhood edicts about washing his hands with soap and avoiding people with the flu.

Still, the intellectual progressions depicted in Mr. Shawn’s “Aunt Dan and Lemon” and “The Designated Mourner” are more jarring in their accretion of details. (In the former play, a fragile young girl embraces several tenets of Nazism after falling under the sway of a glamorous mentor.) Messrs. Shawn and Elliott strive to make the Traveler an incarnation of certain societal trends, but in so doing, they strip him of nearly every useful identifying characteristic beyond those of an upper-class New York City aesthete.

For all his precision in describing any number of interactions, the Traveler studiously avoids using any gender-specific names or pronouns when describing current or former love interests. In fact, a great deal about him is left undisclosed, from his career to the countries he visits. Mr. Shawn’s series of navel-gazing evaluations bring to mind Spalding Gray, but the very real and very messy particulars of Gray’s life were always an essential component of his work. By focusing so hard on making the Traveler one of us, the creators never sufficiently make him one of anybody. (This is not a criticism of the central performance. Mr. Shawn, an underrated actor often used for sputtering comic relief, uses his familiar persona — engaged, articulate, a bit maladroit — to deceptively amiable effect.)

The original 1990 Public Theatre production — to say nothing of the intimate shows that preceded it, in which Mr. Shawn performed “The Fever” in guests’ apartments for a dozen or so people at a time — was devoid of any lighting or sound effects, and here Mr. Elliott overcompensates on this score. The segues between the Traveler’s paranoid reveries and his more measured reminiscences are telegraphed with a few too many bells and whistles: Mr. Shawn’s voice takes on a deathly (and amplified) husk, the lights dim, sound effects seep in. These stretches are plenty creepy enough without the technical assistance, and in their newly augmented form, they allow the audience to maintain an all too healthy distance.

In a typically surreal moment, the Traveler describes finding a copy of “Das Kapital” anonymously deposited on his doorstep. While thumbing through it, he is drawn to Marx’s concept of “fetishism of commodities.” “I wanted to understand that weird-sounding phrase,” he says, “but I could tell that, to understand it, your whole life would probably have to change.” His attempt at comprehension fizzles out after a few days; his life remains unchanged. This concept resurfaces through an extended nightmare sequence in which he describes being jailed and confronted with a book that cannot be shrugged off so easily, a sort of Cultural Revolution “This Is Your Life” that enumerates his bourgeois sins.

That champagne isn’t sitting so comfortably in our bellies anymore. Surely this isn’t our life, is it? Mr. Shawn refuses to answer. He bounds out of the theater immediately after “The Fever” concludes, and stands waiting in the lobby for further chitchat. The Traveler is, once again, one of us.

Until March 3 (410 W. 42nd St., between Ninth and Tenth avenues, 212-279-4200).