In a small and special space at Port City Center, Pure Theatre launched itself as Charleston's newest theater company some months ago.

They made the brave decision that Charleston is ready for the Southeastern premiere of Neil LaBute's "The Mercy Seat," which opened Thursday night to a sold-out crowd that remained rapt throughout a riveting 100 minutes.

This current hot property is nothing if not searing, one of those scripts that insists on your being uncomfortable, questioning not only what is going on before your eyes, but yourself, your value system, your relationships. Be honest, now. What better time for a dose of truth serum than Sept. 12, 2001?

Rodney Rogers plays with precisely the right combination of endearing vulnerability and crass opportunism Ben Harcourt, the original married man caught with his pants down in his lover's apartment the morning of the terrorist attack on the Twin Towers -- where he was supposed to be, hard at work in his office, and where he has yet to tell his family he wasn't.

The object of his affection is his high-powered boss, Abby Prescott, some years older, some years wiser and in some ways right tired of her position as The Other Woman. Sharon Graci offers an uncannily authentic portrayal of a woman seeing her man as though for the first time in the three-year affair -- and is not at all carried away, or not carried away enough to comply with his brilliant idea of using 9-11 as a "meal ticket" to ride off into the sunset.

Director Franklin Ashley, an award-winning playwright and College of Charleston professor of playwriting, uses with economy and style the long and narrow stage area, taking advantage of every inch of a set gleaming with understated New York glitz: Persian rug, buttery leather, sterling cocktail shaker.

The barbs, sarcasms, ironies, accusations fly in a conversation that refers only obliquely to this sudden and entirely unexpected, life-changing event; if you did not already know "what happened" means the events of that fateful day, you could let the setting dawn.

But the sexually charged sparring allows the nature of this illicit affair to dawn, on the two characters as well as the sometimes pop-eyed audience, and to streak across the ashen sky to harsh reality.

The two supremely gifted actors and the experienced director make it happen.