The ultimate test for any work of art is whether it moves us. In theater, even the most famously clever and cerebral writers, such as Tom Stoppard and Stephen Sondheim, became giants because of the visceral punch of their plays and musicals — the poignance and excitement and joy they deliver, and their recognition of the heart’s primacy in the human experience.

This is also true of Anton Chekhov’s work, which is why I was immediately nervous when I learned that Andrew Scott, a very fine Irish actor with numerous stage and screen credits — the most widely known being “Fleabag,” a British TV series — was starring at London in a new variation on “Uncle Vanya” in which he played all the parts. That choice seemed destined to dilute the emotional potency of a play that finds synergy in the interaction between beautifully drawn characters, each distinct in his or her suffering and yearning.

Other performers have taken on similar challenges: In 2013, I saw Alan Cumming in a stripped-down “Macbeth” in which he juggled all the major roles, though smaller characters were eliminated and the script cut accordingly. Still, I was more impressed by the effort and skill Mr. Cumming applied to the task, and by his sheer chutzpah, than I was touched or chilled by his performance.

I had a similar reaction to Mr. Scott in “Vanya,” as the new take on Chekhov’s classic is titled. Now running off-Broadway, the production features a script by Simon Stephens, a British playwright who has won acclaim here and abroad for plays such as “Heisenberg” and “The Curious Incident of the Dog in the Night-Time,” as well as adaptations of other works by Chekhov, Ibsen, and Brecht.

Messrs. Scott and Stephens are listed in the program, along with director Sam Yates and designer Rosanna Vize, as co-creators of “Vanya,” and the collaborative process behind this one-man show is evident from the start, when a simply dressed Mr. Scott enters and begins fiddling with the lighting.

The play’s comedic elements are emphasized in the early stages of the production, which runs 100 minutes with no intermission, during which Mr. Scott is constantly present and extremely busy. His Vanya is mostly referred to by his given name, Ivan; other character names are anglicized, and there are nods to Mr. Scott’s native country: The nurse and housekeeper at Vanya’s estate is called Maureen, and Mr. Scott gives her a distinct brogue that is softened only slightly for the other parts.

Vanya’s pompous brother-in-law, Alexander, who has upended life at the estate by visiting with Helena, the beautiful young woman he married after Vanya’s sister died, is a filmmaker here rather than a professor, and other touches reinforce a contemporary vibe: Mr. Scott’s teal shirt suggests modern medical garb, especially when he is playing Michael, the doctor who turns up to tend to the hypochondriacal Alexander but really lusts for Helena.

Mr. Scott uses props to accommodate shifts between characters; Michael, for instance, bounces a tennis ball, while Sonia, Alexander’s long-suffering daughter and Vanya’s devoted helper, carries a dish towel. Vanya dons sunglasses at points, and wields a digital device that emits goofy, abrasive sound effects.

The most effective, and affecting, moments are generally the quieter ones. When Michael confesses his feelings to Helena in hushed tones, their exchange, even depicted by Mr. Scott alone, is entirely credible, and quite sexy. The simulated lovemaking that follows is a bit awkward, until Vanya interrupts, hilariously.

Even during passages like this, I found myself admiring the star’s technique, which is impeccable throughout, more than feeling Vanya’s pain, or that of any of the other characters. I left a preview of this “Vanya” feeling not so much haunted or shattered as exhausted — though surely not as much as Mr. Scott was.