(L to R) Estelle Parsons as Alexandra and Stephen Spinella as Chris in Arena Stage at the Mead Center for American Theater’s production of The Velocity of Autumn September 6-October 20, 2013. Photo by Teresa Wood. (Teresa Wood)

The part has bravura written all over it: An octogenarian iconoclast is so enraged at her children’s efforts to send her to an old-age home that she barricades herself in her Brooklyn brownstone and booby traps it with homemade bombs.

It’s written for an actress with heat in her eyes and a fire in her belly, qualities radiating from Estelle Parsons in “The Velocity of Autumn,” Eric Coble’s overly contrived if topically relevant dramedy about the terror of having one’s autonomy stolen in the dimming light.

Parsons and her “Velocity” acting partner, the finely, tightly wound Stephen Spinella, execute with ease the transformations into the immovable mother and aggrieved son who battle it out in Arena Stage’s Kreeger Theater. This illusion of effortlessness lets you know that you’re in the presence of actors of the top rank. And under Molly Smith’s unassailable direction, the clash Coble illuminates does manage to touch nerves exposed in the many seemingly no-win debates across America over what’s best for a relative no longer at her sharpest.

This point of anguishing contention is reasonable fodder for earnest drama, and Coble’s 95-minute play contains some lovely, wistful passages about the broken emotional contract between an independent-minded woman and a scarred son who desperately needed to put distance between them. Still, “The Velocity of Autumn” trusts an audience to invest itself only so far. In an effort to pump up the tension, Coble employs a plot device better suited to an absurdist drama than a naturalistic one and in so doing, renders the enterprise histrionic and sillier than it deserves.

If you can view the threat of Parsons’s Alexandra as merely a vivid poetic expression for all the frustrations of old age, then perhaps “The Velocity of Autumn” will hold you. I had trouble with it, because the conceit prompts the only question the play asks: Will Alexandra blow herself, her son and the brownstone — meticulously realized by set designer Eugene Lee — to kingdom come? As her standoff with Spinella’s Chris drags on, the answer seems as if it becomes less and less interesting.

‘The Velocity of Autumn’ by Eric Coble at Arena Stage through Oct. 20. Starring Estelle Parsons and Stephen Spinella. Directed by Molly Smith. (Courtesy Arena Stage/The Washington Post)

The result is the inverse, in a sense, of another real-time play about a mother, a grown child and the threat of annihilation: “ ’Night, Mother,” Marsha Norman’s Pulitzer-winning, two-character play, in which a woman drowning in disappointment announces to her elderly mother that, on this evening, she intends to kill herself. Although that more harrowing piece, too, flirts at times with heavy-handedness, the terrible ending that’s promised doesn’t come across as fulfillment of a stunt. Over the course of “ ’Night, Mother,” Norman deftly unfolds an argument about death that comes to seem a logical, if awful, way out for the daughter, Jessie.

“The Velocity of Autumn,” on the other hand, reveals that Alexandra’s gambit is merely manipulative theatrics. Surrounded by dozens of molotov cocktails and brandishing a lighter, Parsons holds Chris and the audience at bay. Alexandra amusingly runs through the laundry list of reasons not to grow old: the joint aches, the loneliness, the fading short-term memory, the indignity of the lengthening senior moment. But as she lets down her guard amid the flammable liquids, you might wonder: Why doesn’t able-bodied Chris simply wrestle away the lighter?

What’s more, Alexandra seems far more mentally and physically together than the alarm bells sounded by her children would indicate. We’re told that she has alienated her entire bridge club with her suspicions that they’re all cheating and that she went blank after a visit to the grocery store. As she points out, however, her house is clean and the bills are paid. Aside from a diabolical imagination — she fills makeshift incendiary devices with photographic developing fluid — what’s the rush?

“The Velocity of Autumn” packs as much of its agenda with the healing of Chris as with what to do with Alexandra. And it is in the discovery of his demons that the play exhibits some subtler textures. The youngest of Alexandra’s three children, pony-tailed Chris has been summoned from out West to climb into an upper-story window and confront the mother he has avoided seeing for 20 years. And in the process, he enters into a deeper conversation about the unfinished business in his unhappy life.

Smith sensitively steers Parsons and Spinella through the tentative dance steps of reconciliation, and Coble gives each of the actors ample opportunity to explain who these people were to each other and what they could mean to each other again. Linda Cho’s costumes, too, underline the vibrant colors of Alexandra’s personality and the more muted aspects of Chris’s.

Arena Stage is advertising “The Velocity of Autumn” as a “pre-Broadway engagement.” Whether the production has those kinds of legs, I have no idea. Which projects are determined these days to be Broadway-appropriate is more mystifying than ever, although it should be added that the team of Parsons and Spinella feels right for almost any occasion.

The Velocity of Autumn

by Eric Coble. Directed by Molly Smith. Set, Eugene Lee; costumes, Linda Cho; lighting, Rui Rita; sound, Darron L. West; wig design, Paul Huntley. About 1 hour, 25 minutes. Through Oct. 20 at Arena Stage, 1101 Sixth St. SW. 202-488-3300. www.arenastage.org.