Listen. Listen harder. That’s what the British playwright Howard Barker needs you to do during “Gary the Thief” and “Plevna: Meditations on Hatred,” his two short, dense plays produced by the Potomac Theater Project/NYC at Atlantic Stage 2.

Theater is elastic, he reminds us, and proceeds to stretch our definitions of it. Mr. Barker, also a poet, describes his work as a Theater of Catastrophe in which, as it says in the program, “no attempt is made to satisfy any demand for clarity or the deceptive simplicity of a single message.”

Indeed. These two pieces, written as poems and delivered as monologues, come at you in a rush and can be fragmentary and elusive. Don’t be surprised if you miss things. But also don’t be surprised if Mr. Barker’s blunt lyricism lingers in your mind.

“I hate the weak/And whimper in the presence/Of the strong,” says Gary the Thief. A working-class hoodlum, Gary kills a baby, goes to prison (with its “dirty glamour attaching to/Insane and paltry acts”) and is courted by powerful people. At the end — impossibility of spoiler alert — the “cold has riddled his youth/And the ice has quarried his teeth,” but he sets off to be a prophet.

Plot, obviously, doesn’t make “Gary the Thief” run. (Good thing: chunks of it passed me right by.) The poetry — slippery and impressionistic — does, and the play, receiving its world premiere in this production, directed by Richard Romagnoli, is lucky to have the actor Robert Emmet Lunney to deliver it.

Mr. Lunney makes visceral what might have been abstract. He varies the colors of his voice and his accent: he can be prim, even schoolmarmish when he narrates, but as Gary the Thief he has a Cockney swagger and impacted rage. Gary’s stare is ferocious. (Reader, he scared me.)

Mr. Lunney, in a dark suit, performs on a bare black set with only a hint of theatrical artifice: a wry proscenium arch near the back of the stage. It’s all very spare and tasteful — he seems like a pearl nestled in a velvet jewel case — but it creates a respectful hush that tames the play.

Still, Mr. Lunney carries the day, making “Gary” the more dramatically satisfying of the two pieces on this 50-minute program. In “Plevna: Meditations on Hatred,” receiving its New York premiere, Mr. Romagnoli also keeps the stage bare, save for a few chairs. But here he has a conceit, which might be trite if it were more insistent.

For this monologue about war and the nasty things civilians do, the actor, Alex Draper, wears a tux and brandishes a highball glass. He surveys and anatomizes the wreckage of battle as if pointing out the vomit after a drunken party.

Plevna was the site of a siege in 1877 in the Russo-Turkish war. Not that Mr. Barker tells you that and not that he means his play, with its shifting perspectives, to be restricted to one historical event.

Mr. Draper, though, doesn’t have Mr. Lunney’s range, and his slow build to anger seems a bit mechanical. Squint, and he’s just a guy reciting poetry onstage. But that poetry compels. Passages stick: “Who was drowned by the snow/Which rose to the mouth of the sleeping sentry/The thaw will show.”

“Gary the Thief” and “Plevna: Meditations on Hatred” continue through July 31 at Atlantic Stage 2, 330 West 16th Street, Chelsea; (212) 279-4200, ticketcentral.com.