Three hours with a dysfunctional family might sound more like a preview of Thanksgiving coming attractions than a night on the town. But the Weston clan isn't just any family.

While the fact they're not yours is something to be thankful for, indeed, their hilarious and horrible appeal lies in the way playwright Tracy Letts has used them to explore some of the most compelling questions of the human condition: Why do we inflict our worst damage on those we love? What is there to choose between self-delusion and savage truth? Why is it so hard for us to learn from the past? And as the play quotes T.S. Eliot, if "life is so long," what are the advantages of survival?

"August" begins with the three adult Weston sisters having been summoned to the Oklahoma family home by matriarch Violet Weston. Their father, dissipated poet Beverly Weston, has disappeared and is feared dead. The eldest daughter, Barbara, drags in her broken marriage to Bill and her rebellious teenage daughter, Jean; the youngest, Karen, arrives with her shady businessman fiance Steve. There's also Ivy, the middle girl who never left town. Violet's sister Mattie Fae, her husband Charlie and son Little Charles show up, and the proceedings are overseen by Johnna, the quiet Native American housekeeper.

That weary Beverly (a gemlike and too-brief performance by John Amplas) has opted out of the ongoing Weston drama is the least surprising thing that emerges from what follows. One crushing revelation after another -- drug addiction, abuse, incest -- falls to earth like a bomb, severing relationships on all sides.

With such goings-on, "August" could collapse into camp. But director John Shepard has kept the performances in the Playhouse Rep production taut, the exchanges crisp and the pacing even and brisk, so that the drama and humor unfold rather than being forced and characters don't descend into caricature.

These efforts set off an excellent cast, led by Mary Rawson's Violet. She ensures we see not just the character's terrible will to deny responsibility for the pain she causes, but also how she can be charming, affectionate and as fragile as a child.

Johnna, part audience proxy and part silent Greek chorus, is performed by Erika Cuenca as everpresent without being obtrusive, reminding us that we might empathize with Violet and her family even as we deplore their actions.

Dennis Schebetta is sweetly hapless as manchild Little Charles, and Paul Anthony Reynolds makes a big impression with the small part of Sheriff Deon, who remembers, and longs for, the Weston girls of his youth. Sharon Brady and Weston Blakesley make an excellent couple as Mattie Fae and Charlie Aiken, both fully drawn characters whose marriage may not survive the Weston legacy.

As 15-year-old Jean, Courtney Neville shows teenage self-involvement and vulnerability to perfection, displaying a professionalism beyond her young years (she is a recent Point Park graduate). David Whalen has a difficult part as Bill, Barbara's husband, and portrays him as a man who hovers uncertainly between decent and a bit repugnant.

Meghan Malloy slightly overdoes it as Karen, a woman grasping desperately for some joy. But her shrill insistence on her own happiness ("I'm going to Belize!" she shrieks, not once, but twice) serves to point up the fact that she already knows it is founded on nothing real. Mark D. Staley ably plays Steve with an oily sheen that barely obscures his narcissism -- he answers his cell phone in the midst of a family prayer of mourning. Elizabeth Ruelas gamely tackles another difficult part as Ivy, the unloved and graceless daughter, giving her a quiet determination to escape that, in the last act, is turned against her with devastating results.

As the strongest daughter, Kathleen Turco-Lyon imbues Barbara with a wholly believable ferocity and capacity for violence, which we gradually see she has inherited from her mother. Ms. Turco-Lyon makes no missteps here, treading surely among profane humor, physical comedy and drama.

The set design in the confines of Pittsburgh Playhouse's Rauh Theatre is by Stephanie Mayer-Staley and deserves mention for its ability to be both spacious and claustrophobic.

Ultimately, though, "August" is all about Violet, and Ms. Rawson's performance thoroughly and rightly dominates the play. The character and performance owe much to forerunners such as O'Neill's "Long Day's Journey Into Night" and Shakespearean roles.

At the end of the first act, her tongue both loosened and numbed by pills, Violet struggles to articulate her failed attempts to make sense of her life with the repeated phrase, "And then you're here." It echoes King Lear's repetition of "Never, never, never ..." as he mourns his daughter Cordelia's death, and evokes the same terror of meaninglessness and ultimate loss. Where is here? What does being here mean, if anything? Mr. Letts' play asks these questions -- and for that, we must also be thankful.